The treatment of Wilms' tumor is based on initial surgical removal followed by clinical and histologic staging. Chemotherapy provides the major adjunctive therapy in virtually all Wilms' tumors, radiotherapy being used in some situations. Exceptions to this are the treatment of bilateral Wilms' tumors and large intracaval extension. Bilateral Wilms' tumor is treated with initial biopsy and staging, adjunctive chemotherapy, and/or radiation therapy and bilateral partial nephrectomy after there is maximum resolution of tumor. Similarly, extensive caval extension of tumor may be treated preoperatively with chemotherapy and radiotherapy followed by resection. Nephroblastomatosis, a precursor of Wilms' tumor, is a common associated finding at exploration. It requires alteration in management and may change the prognosis. Sarcomas of the kidney and congenital mesoblastic nephroma represent the spectrum of severity of solid renal masses in children. Neuroblastoma is the most common solid tumor in children, and its prognosis is largely dependent on the age of the patient and the stage of disease. Chemotherapy and radiotherapy is adjunctive treatments have been disappointing. Immunotherapy holds some promise for the future. Testicular tumors are unusual in children. Those that occur in infancy are most often benign teratomas that require orchiectomy alone. Malignant germ cell tumors in children are most often yolk sac tumors and respond to surgery and chemotherapy. Lymph node dissection is indicated only in paratesticular rhabdomyasarcoma. Other genitourinary rhabdomyasarcomas occur in the bladder, prostate, vagina, and uterus. After maximum decrease in tumor volume with chemotherapy and radiotherapy, surgical exploration and resection of remaining tumor probably represent the best form of treatment. Organ-sparing procedures should be carefully selected in that they may worsen the prognosis.