Romania consists of four major areas where Mesozoic and older rocks crop out: the Southern Carpathians, the Eastern Carpathians, the Apuseni Mountains, and Dobrogea. Late Tertiary sedimentary rocks cover connections between these four areas and rest on older rocks in the Pannonian and Transylvanian Basins and in the Skythian (Russian) and Moesian Platforms. Although the Carpathian orogenic belt appears to form a continuous convex-east arc through Romania, this arc was created through a series of structural events that began in Triassic time and are now in their final stages. The Southern Carpathians consist of three structural and paleogeographic units. They are, from east to west, the Danubian terrane, the Severin nappe, and the Getic terrane. The Danubian and Getic terranes consist of shallow-water marine and nonmarine Mesozoic rocks that rest on Paleozoic and Precambrian sedimentary and ciystalline rocks. Rocks of the Getic terrane have been thrust relatively eastward over rocks of the Danubian terrane along the Getic thrust fault. Between the Getic and Danubian rocks is a complicated thin slice of flysch and associated rocks of Late Jurassic to Late Cretaceous age, locally containing mafic and ultramafic rocks at their base, belonging to the Severin nappe. Rocks of the Severin nappe may represent remnants of an oceanic terrane that probably continued eastward into the flysch terrane of the Eastern Carpathians. The date of emplacement of the Getic and Severin nappes is not firmly established, but most likely it occurred during latest Cretaceous to earliest Tertiary time. The Eastern Carpathians consist of two main paleogeographic and structural units. From east to west, they are the inner crystalline zone and the outer Flysch zone. Mesozoic rocks of the inner crystalline zone are primarily shallow marine or nonmarine and rest on crystalline rocks of Paleozoic and Precambrian age. They are similar to rocks of the Southern Carpathians. A direct continuation is not possible, however, because Tertiary rocks of the Brasov depression conceal the relation between the two units. Structurally, the inner crystalline zone consists of a sequence of relatively east-directed thrust slices; all but the uppermost slice contain pre-Mesozoic crystalline rocks. From the base to the top, the main tectonic units are the Bretila Unit, the Sub-Bucovinian nappe, the Bucovinian nappe, and the Transylvanian nappes. The Transylvanian nappes consist of isolated masses of Mesozoic sedimentary rocks, some incorporated in wildflysch; they were probably emplaced by gravity during Early Cretaceous time. Thrusting of the lower three units is well dated and occurred during late Albian to early Vraconian time. During the same event, the crystalline nappes were thrust relatively eastward over the westernmost nappes of the Flysch zone. The Flysch zone contains sedimentary rocks of Late Jurassic to late Sarmatian age, with the older rocks (Jurassic and Cretaceous) present mainly in the western part of the zone. The Flysch zone consists of seven nappes: they are, from west to east, the Black Flysch Unit, the Ceahleau nappe, the Curbicortical nappe, the Audia nappe, the Tarcau nappe, the Marginal Folds Unit, and the Sub-Carpathian nappe. Stratigraphic units in the flysch nappes change markedly from one nappe to the next; this change can best be explained in terms of the migration of the axis of flysch deposition outward in time. Migration of the axis of the flysch basin can be further interpreted to result from westward underthrusting of the flysch zone beneath the inner crystalline zone and formation of nappes from west to east. Deformation of the Flysch zone extended over a long period, probably from Albian to Holocene time. Pleistocene rocks are folded at the south end of the Flysch zone; these folds lie above a small region of deep-focus (to 200 km) earthquakes, which suggests that underthrusting is still active but is in its last stages. The Apuseni Mountains are a group of mountains in central Romania north of the Southern Carpathians and west of the Transylvanian Basin. They consist of two different structural elements — the Northern Apuseni and Southern Apuseni Mountains. Rocks in the Northern Apuseni Mountains consist of Mesozoic shallow-marine and nonmarine sedimentary rocks overlying Paleozoic and Precambrian sedimentary and metamorphic rocks. North-directed thrust faults, nearly all involving pre-Mesozoic basement rocks, cut the rocks in the southern part of the Northern Apuseni Mountains. The nine thrust plates can be divided into the Codru nappes group to the north, which contains primarily Mesozoic rocks, and the Crystalline or Biharia nappes group to the south, which contains only pre-Mesozoic rocks. The nappes were emplaced during Late Cretaceous time, but only the northernmost nappes are clearly dated as being late Turonian to early Coniacian in age. The Southern Apuseni Mountains consist of several large bodies of mafic and rare ultramafic rocks, probably representing a Middle Jurassic ophiolite sequence, and thick sequences of flysch, wildflysch, and molasse of Late Jurassic to Late Cretaceous age. The stratigraphy and structure of the sedimentary rocks are poorly known but appear to represent several different sedimentary basins that have been brought together by a long series of Cretaceous structural events. Structural events are recorded in Aptian, Albian, Turonian, Santonian(?), and Maestrichtian time; the earlier structural events were vergent to the south and the later events to the north, giving the Southern Apuseni Mountains a crude fan structure. The Dobrogea area consists of a group of low mountains in southeastern Romania east of the main Carpathian chain. Dobrogea can be divided into four northwest-trending structural zones, each bounded by faults of probable large displacements. (1) The Pre-Dobrogea depression is buried beneath the Holocene sediments of the Danube Delta north of Dobrogea proper. Its north flank is the Skythian Platform, and its south flank is marked by a south-dipping thrust(?) fault. Structurally, it is an asymmetric syncline with a steep south flank and is filled with a thick sequence of Jurassic rocks. (2) North Dobrogea contains a basement of rocks that were deformed and metamorphosed in Hercynian time; they are overlain by a thick sequence of alpine-type Mesozoic rocks. Structurally, the rocks are thrown into northeast-directed folds and thrusts, probably formed either at the end of Jurassic time or in late Early Cretaceous time. (3) Central Dobrogea contains a basement of Precambrian metamorphic rocks that are overlain by only weakly folded Jurassic rocks. (4) South Dobrogea contains rocks similar to Central Dobrogea and dips gently south, forming the east margin of the Moesian Platform. The structural units in Dobrogea can be traced in the subsurface toward the Carpathians but become buried by late Tertiary rocks of the Carpathian foredeep. Only the Pre-Dobrogea depression can be traced east of the Carpathians into Poland; the trend of the depression is linear and is unaffected by the arc of the Carpathians. The Pannonian and Transylvania Basins are superposed on the structural elements of the Carpathians. They clearly represent post-tectonic basins, partly created by extension in middle and late Tertiary time. Unfortunately, these Tertiary basins conceal the relations between the structural elements of the Carpathian orogen.