The genetic diversity of the envelope glycoprotein of human immunodeficiency virus type 1 (HIV-1) isolates was studied. HIV-1 isolates were obtained from eight countries in Africa: Djibouti, Gabon, Kenya, Senegal, Somalia, Uganda, Zaire, and Zambia. The DNA sequences encoding the complete HIV-1 envelope protein were PCR amplified and sequenced. Phylogenetic relationships among the 21 sequences from this study and the 32 previously published full-length env HIV-1 sequences were determined. Twenty of the newly sequenced African isolates could be assigned to envelope subtypes A, C, D, and G. One isolate, collected in Zambia, did not belong to any of the eight previously described subtypes and may represent a prototype sequence of its envelope subtype. The phylogenetic classification of these isolates was strongly supported by bootstrapping and the congruence of trees generated by either distance methods or maximum parsimony analysis. The data presented in this study confirm the existence of several genetic subtypes within the global HIV epidemic and broaden the genetic variability previously observed for envelope subtypes. The geographic spread of different subtypes was shown to be substantial, and the notion of cocirculation of subtypes was reinforced.