The frequency of developmental defects and displasticity characters in children with nephroblastoma was determined in two groups--with early, up to 2 years manifestation of the tumor (ENB), in 40 patients, and with advanced nephroblastoma (ANB), in 59 patients (manifestation of the disease after 2 years). The data were correlated with control groups adequate for age (130 children). The frequency of serious developmental defects was higher in ANB group (20%) than in ENB group (7%). Over a half of developmental defects were hemihypertrophy and doubling of organs. One case of a child with the combination of nephroblastoma and Smith-Lemli-Opitz syndrome was defined. In ANB group an increased frequency of asymmetry in the conjugate organs (foot, hand, middle finger, ears) was found. Its direction is correlated with tumor localization (tumor site). In ENB group no analogous effect was shown. The data obtained present phenotype characteristics of groups with early and late manifestation of the disease which are probably different in their genesis and thus, their identification is necessary for the adequate medicogenetic consultation (examination).