Aim. Epidemiologic examination of the case of group HIV-1 infection based on data obtained by general diagnostics methods for confirmation of the investigation hypothesis of deliberate HIV infection during heterosexual intercourse. Materials and methods. Sera samples from 8 HIV infected patients (5 female and 3 male) from Veliky Novgorod sent for epidemiologic investigation were used. Determination was carried out based on 1285 nt sequence analysis of polymerase gene segment (pol). Results. The study allowed to identify HIV in clinical samples sent to the expertise and establish phylogenetic connections between virus isolates obtained from both target and control group patients. Analysis of the results allowed to isolate samples grouped in a separate cluster that indicates tight cordial connections between the vims isolates from clinical material of these patients. Patients of the target group were infected with HIV-1 isolate ofthe circulating recombinant form CRF03_AB from the same origin that is confirmed by high homology ofthe nucleotide sequences. Conclusion. Epidemiologic investigation of a group case of HIV-1 infection has determined that the infection of the women of the target group occurred from the same source. Phylogenetic analysis results indicate the presence of an epidemiologic connection within the examined group that confirms the HIV infection transmission and conclusions ofthe investigation. Use of molecular-phylogenetic analysis of data obtained by laboratory diagnostics methods of HIV resistance to antiretroviral preparations allows with anamnestic and investigation information (in the context of available evidence) to investigate cases of HIV infection.