The purpose of this study was to determine whether yeast isolates from mothers and their new-borns are of the same genotype. In this investigation, 103 parturient mothers and their children were examined for colonization by yeasts by sampling the vaginal secretions at delivery and by taking swabs from the oral mucosa and the anus of the children on the third day after parturition. The samples were cultured on Sabouraud glucoseagar and incubated for 48 h at 37 degrees C. Differentiation of the isolates was achieved biochemically by means of the Vitek AMS system and morphologically on rice extract agar. Subsequently DNA fingerprinting analysis was carried out by means of pulsed-field gel electrophoresis (PFGE). In six cases we could prove the presence of Candida spp. in the mothers as well as in their children. In all cases the strains isolated from mother and child showed the same banding pattern. Likewise, the strains isolated from the vaginal secretion and the vaginal epithelium of individual women were identical. The differences observed between strains isolated from different women were small to middling. This shows PFGE to be an efficient procedure to demonstrate the relation between strains derived from mothers and their newborns.