In a bid to determine the HIV-1 subtype variants in transmission in Nairobi and its possible association with clinical status, we screened 207 confirmed HIV-1 positive patients visiting HIV/AIDS laboratory at the Virus Research Centre in Nairobi between January and March 1994. We used a selfmade ELISA obtained from an established panel of HIV-1 V3 loop peptides (ANRS, France) and derived from seven isolates: MN, HXB2, SC, Z6, Z2, ELI and CDC4. Test samples were obtained from 95 blood donors and medical examination attendees, 57 patients with chronic diarrhoea, 31 confirmed pulmonary tuberculosis, 16 with pneumonia and 12 herpes zoster. Out of the total, 21.5% had antibodies against the MN strain, 19.1% had against the Z2 strain while reaction against the HXB2 strain was observed in 17.2%. SC, CDC4, Z6 and ELI had prevalences of 11.5%, 6.2%, 5.3% and 3.8% respectively. Fifteen per cent of the tested sera showed no reaction to any of the used peptides. Strong and significant associations were observed between the total number of strains a sample react to and the clinical state. We infer that both the North American consensus strains (MN and HXB2) and the African isolates (Z2 and Z6) are predominant in Nairobi. The correlation between antibody reactivity and clinical state is an interesting observation that necessitates an expanded study and, the use of strain specific peptides maybe a sensitive and easier method for use for molecular epidemiological purposes. PIP: During January-March 1994, in Nairobi, Kenya, the sera of pre-university students, suspected AIDS/advanced HIV-infection cases, and blood donors were screened for HIV-1 antibodies at the Virus Research Centre. All confirmed HIV-1 positive samples were categorized according to the patient's clinical status. A self-made ELISA was obtained from an established panel of HIV-1 V3 loop peptides and derived from seven isolates (MN and HXB2 [North American strains], SC, CDC4, Z2 and Z6 [African strains], and ELI). The sera of the 22 confirmed HIV-1 negative students were used as negative controls. There were 207 confirmed HIV-1 cases (95 blood donors and 112 suspected AIDS/advanced HIV-infection cases). 64 (31%) and 112 (54%) samples reacted to at least 3 strains and no more than 2 strains, respectively. The remaining 31 (15%) samples did not react to any of the 7 peptide strains. Samples with CD4 cell counts greater than 500 x 1 million reacted significantly to more peptide strains than those with CD4 counts below 200 x 1 million (88% vs. 7%). Reactivity to specific strains were 21.5% for MN, 19.1% for Z2, 17.2% for HXB2, 11.5% for SC, 6.2% for CDC 4, 5.5% for Z6, and 3.8% for ELI. Anti-HXB2 antibodies were more common in blood donors than suspected AIDS/advanced HIV-infection cases (22% vs. 13%). AIDS/advanced HIV-infection cases were more likely to have no antibodies than blood donors (21% vs. 7%). A significant association existed between the number of peptide strains a patient could react to and the clinical state (p 0.01). Specifically, 77% of samples with no V3 antibodies to the seven strains had AIDS or advanced HIV infection while 55% of those which had cross reactivity with three or more strains were asymptomatic. Further research is needed to better understand this correlation. These findings suggest that use of strain specific peptides may be a sensitive and easier method for use for molecular epidemiological purposes.