Recent studies indicate a favorable outcome with bilateral Wilms' tumor. From 1971 to 1985, ten children between the ages of 6 months and 5 years were treated for this disease. During the early part of the series, five patients had nephrectomy on one side and partial nephrectomy on the other side, and one patient had bilateral partial nephrectomies at the same operation. More recently four patients initially had a biopsy of both tumors and lymph node sampling followed by chemotherapy. At the second-look procedure two patients had multiple biopsies because there was no obvious tumor. Histologically there was no tumor on the third-look procedure in these two patients. Nine patients had a favorable histology of the Wilms' tumor. One patient had a favorable histology on one side and an unfavorable type of histology on the other side. Eight patients are surviving between 6 months and 13 years. Two died of extensive disease within 16 months of diagnosis. One patient had an unfavorable histology. The good results following partial nephrectomies have led us to attempt to conserve additional tissue, as has been done in the last four patients. Our early results suggest biopsy of the tumor followed by chemotherapy, then a second look, and if necessary, third-look procedures may result in preservation of functioning renal tissue.