Purpose: To determine the risk of subsequent carcinomas other than breast, thyroid, and skin, and to identify factors that influence the risk among survivors of childhood cancer. Patients and Methods: Subsequent malignant neoplasm history was determined in 13, 136 participants (surviving ≥ 5 years postmalignancy, diagnosed from 1970 to 1986 at age < 21 years) of the Childhood Cancer Survivor Study to calculate standardized incidence ratios (SIRs), using Surveillance, Epidemiology, and End Results data. Results: In 71 individuals, 71 carcinomas were diagnosed at a median age of 27 years and a median elapsed time of 15 years in the genitourinary system (35%), head and neck area (32%), gastrointestinal tract (23%), and other sites (10%). Fifty-nine patients (83%) had received radiotherapy, and 42 (59%) developed a second malignant neoplasm in a previous radiotherapy field. Risk was significantly elevated following all childhood diagnoses except CNS neoplasms, and was highest following neuroblastoma (SIR = 24.2) and soft tissue sarcoma (SIR = 6.2). Survivors of neuroblastoma had a 329-fold increased risk of renal cell carcinomas; survivors of Hodgkin's lymphoma had a 4.5-fold increased risk of gastrointestinal carcinomas. Significantly elevated risk of head and neck carcinoma occurred in survivors of soft tissue sarcoma (SIR = 22.6), neuroblastoma (SIR = 20.9), and leukemia (SIR = 20.9). Conclusion: Young survivors of childhood cancers are at increased risk of developing subsequent carcinomas typical of later adulthood, underscoring the importance of long-term follow-up and risk-based screening. Follow-up of the cohort is ongoing to determine lifetime risk and delineate individual characteristics that contribute to risk.