In order to obtain more information about the presence of HIV-1 in mononuclear cells of colostrum, research was carried out on both the HIV-1 genome in the cellular fraction of colostrum and the viral antibody in cell-free colostrum of eight anti-HIV-1 seropositive asymptomatic mothers. In five cases cell fractions of the colostrum harbored HIV-1 genome by DNA-DNA and DNA-RNA in situ hybridization, whereas viral antibody were detected in all cell-free colostrum specimens. The data confirms the colostrum as a possible route of HIV-1 infection.