Wegener's granulomatosis (WG) is an uncommon systemic vasculitis that is rarely encountered in children. A 15-year old boy presented with a one-month history of nasal obstruction, hemorrhagic rhinorrhea, malaise, fever, anorexia and weight loss, together with high values of inflammatory markers, microscopic hematuria and progressive decrease of renal functions. Renal biopsy revealed rapidly progressive crescentic glomerulonephritis with rare findings of interstitial and periglomerular granulomas. The diagnosis of WG was established and intravenous methylprednisolone and cyclophosphamide therapy followed by oral application of prednisone and azathioprine led to a complete clinical and laboratory remission of the disease. The second renal biopsy performed after 28 months of treatment did not show any activity of the process. Currently, the boy is without any clinical or laboratory signs of active disease. Since untreated WG has a fatal prognosis, early diagnosis and appropriately aggressive immunosuppressive therapy are necessary for a favorable outcome.