A nephrotic syndrome which appears during the first few months of life always provides a diagnostic challenge. Congenital nephrosis of the Finnish type (CNF) is a distinct, recessively inherited entity provided that the diagnostic criteria are kept strict. Very important but often forgotten is the presence of a large placenta. Among other alterations tubular dilatations are typical histological findings, even if not pathognomonic. Greatly elevated AFP concentration in the amniotic fluid, due to intrauterine proteinuria, offers an unfailing prenatal diagnosis in CNF but is seldom useful in other types. Renal transplantation has radically changed the prognosis of this otherwise lethal disorder. The histopathological diagnosis diffuse mesangial sclerosis (DMS) was supposed to represent another etiological entity, probably also autosomal recessive. It, however, seems to be heterogenous. The Drash syndrome (nephrotic syndrome, male pseudohermaphroditism and Wilms' tumor) has interesting connections with this group. The number of cases of congenital, infantile and/or familial nephrotic syndromes other than CNF and DMS seems to be surprisingly large. Their exact classification is still not possible. Even if late, "infantile" onset rules out the diagnosis of CNF, many etiological alternatives remain for the "congenital" cases.