The only two HIV-1 strains (ANT70 and MVP5180) reported to date from Cameroon are members of the outlier clade (group O). In this study, we assessed the prevalence of group O viruses and other HIV-1 subtypes in Cameroon. A phylogenetic analysis of 18 HIV-1 strains isolated from seropositive individuals from Yaoundé and Douala, Cameroon. A 900 base-pair fragment of the env gene coding for V3, V4, V5, and the beginning of gp41 of 17 out of 18 HIV-1 isolates from Cameroon was amplified, cloned and sequenced using polymerase chain reaction. A phylogenetic tree was constructed. The overall env nucleotide sequence divergence among the Cameroon isolates ranged from 6.1 to 27.5%. In a phylogenetic tree, six subtypes were identified when compared with 23 reference strains of different geographic origin. Of these 17 Cameroonian strains, 11 (61%) were of subtype A of which the interpatient distances at the sequence level varied from 6.1% to 18.3% (average, 11.9%). Three (17%) strains were of subtype F, and the other three strains (6% each) belonged to subtypes B, E and H, respectively. The remaining isolate was classified as belonging to group O, on the basis of the sequence of part of the pol gene. A very broad spectrum of different tetrameric amino-acid sequences was observed at the apex of the V3 loop. Eleven strains contained the tetrameric globally predominant GPGQ sequence at the tip of the V3 motif. Two strains had the GPGR sequence typical of the American and European HIV-1 strains. The remaining tetrameric sequences included GPGS, GSGQ, GRGQ, and GLGR. These findings on a limited number of viruses suggest extensive env gene diversity of HIV-1 strains from Cameroon, and could have implications for vaccine development in Africa.