Two cases of Wilms' tumor in adolescent males are presented. The clinical and radiographic findings were unusual and both presented atypical gross and microscopic features that could be correlated with the radiographic findings. Histologic examination of both tumors showed evidence of tubular and glomerular maturation, a feature usually associated with Wilms' tumors of early infancy. One of the tumors contained a large amount of cartilage and bone. The other was grossly cystic and incorporated some features of multilocular cystadenoma, a benign metanephric tumor.