New sequence data from the D6 region of 28S rRNA and rDNA are presented for 28 species of molluscs and two annelids. These sequences were analyzed along with previously published molluscan sequences. Five of the molluscan classes were represented: Gastropoda, Cephalopoda, Bivalvia, Scaphopoda, and Polyplacophora, the last two by only one species each. Allowing for presumed long branch effects of Helicinidae, Patellidae, and the annelids, cladistic analysis supported monophyly of the following groups: Cephalopoda, Nautiloida, Coleoida, Gastropoda, Apogastropoda, Caenogastropoda, Neogastropoda, Rissooidea, Pulmonata, Stylommatophora, and a subset of Heterodonta including Sphaeriidae, Dreissenidae, and Veneridae but not Cardiidae. No resolution of relationships among molluscan classes was obtained.