Phylogenetic relationships among various primate groups were examined based on sequences of epsilon-globin genes. epsilon-globin genes were sequenced from five species of strepsirhine primates. These sequences were aligned and compared with other known primate epsilon-globin sequences, including data from two additional strepsirhine species, one species of tarsier, 19 species of New World monkeys (representing all extant genera), and five species of catarrhines. In addition, a 2-kb segment upstream of the epsilon-globin gene was sequenced in two of the five strepsirhines examined. This upstream sequence was aligned with five other species of primates for which data are available in this segment. Domestic rabbit and goat were used as outgroups. This analysis supports the monophyly of order Primates but does not support the traditional prosimian grouping of tarsiers, lorisoids, and lemuroids; rather it supports the sister grouping of tarsiers and anthropoids into Haplorhini and the sister grouping of lorisoids and lemuroids into Strepsirhini. The mouse lemur (Microcebus murinus) and dwarf lemur (Cheirogaleus medius) appear to be most closely related to each other, forming a clade with the lemuroids, and are probably not closely related to the lorisoids, as suggested by some morphological studies. Analysis of the epsilon-globin data supports the hypothesis that the aye-aye (Daubentonia madagascariensis) shares a sister-group relationship with other Malagasy strepsirhines (all being classified as lemuroids). Relationships among ceboids agree with findings from a previous epsilon-globin study in which fewer outgroup taxa were employed. Rates of molecular evolution were higher in lorisoids than in lemuroids.