The results of histological, electrophorelic, chromatographic, and chemical studies of hemoglobins of newborn and adult Lemur, Galago, Hapalemur, and Propithecus indicate that major hemoglobins of newborn Prosimii, unlike those of newborn Anthropoidea, cannot be distinguished from the major hemoglobins of adults of the same species. Hemoglobins of newborn and adult Prosimii, like human fetal hemoglobin, are not eluted from red cells after incubation at acid pH and are alkali-resistant. Galago crassicaudarus, Lemur catta, and Hapalemur griseus normally have two major hemoglobins; in each species, both of the major hemoglobins are alkali-resistant. Differences between hemoglobins of Prosimii and Anthropoidea are discussed.