Familial juvenile nephronophthisis (FJN) represents an important cause of chronic renal insufficiency in the first two decades of life. Its frequency is reported to vary between 7 and 20% of all cases of terminal renal failure in childhood. Usually the onset is insidious, with polyuria, polydipsia and anaemia being the main clinical features. The diagnosis is based on clinical, laboratory and pathological findings. The purpose of our report is to emphasize the importance of this pathological entity with respect to the clinical symptoms and signs and diagnostic approach on the basis of the case reports of four patients.