Palpable renal masses presenting in eight newly born babies are described. Three of the masses were primary renal tumours, namely renal dysplasia in two and congenital mesoblastic nephroma in one, while in three neonates the masses were secondary to obstruction, in two in the 'prune belly' anomaly and in one caused by posterior urethral valves. In two of the babies the masses were thought to be renal because of their location and in one following an abnormal intravenous pyelogram. Firm diagnoses were not possible in all our patients because some parents defaulted before investigation was complete. While surgical exploration is often crucial in establishing the diagnosis of an abdominal mass it is possible in certain cases to make a correct diagnosis without surgery.