Mucosal transmissions account for the majority of HIV-1 infections. Identification of the viral characteristics associated with transmission would facilitate vaccine design. This study of HIV strains from transmitting males and their seroconverting female partners found that the males’ genital tract viruses were rarely distinct from the blood variants. The imputed founder viruses in women were genetically similar to both the blood and genital tract variants of their male partners, indicating a lack of evidence for genital tract-specific lineages. These findings suggest that targeting vaccine responses to variants found in blood are likely to also protect from genital tract variants.