We describe human immunodeficiency virus type 1 (HIV-1) diversity in Western Brittany, France, and trace the dissemination of HIV-1 non-B subtype infection. The strategy for HIV-1 subtyping used involved subtype specific enzyme immunoassays, heteroduplex mobility assays and phylogenetic analysis of the sequences of env encoding the V3 loop region. Samples were obtained from 567 patients: 465 (82%) were of subtype B and 66 (11.6%) were not (20 were subtype A, 11 subtype C, four subtype D, seven subtype F, five subtype G and 19 others with circulating recombinant forms: 4CRF01_AE, 11CRF02_AG, 1H, 3CRF11_cpx). These findings are consistent with other studies of French populations. There is an epidemiological correlation between subtype B and homosexual or heterosexual contamination in France and between non-B subtype and heterosexual contamination in Africa.