OBJECTIVE: We used the nationwide Swedish Family-Cancer Database to analyze the risk for adult (15-61 years) brain tumors in offspring through parental cancer probands. Additionally, cancer risks were assessed among siblings of brain tumor probands. METHODS: In offspring and parents, respectively, 5,425 and 20,938 cases of brain tumors were diagnosed between the years 1958 and 1996. Groups of offspring were compared by calculating standardized incidence ratios (SIRs) for brain tumors. RESULTS: Of brain tumor patients, 2.1% had a parent with nervous system cancer; SIRs were 1.7, 2.4, and 2.5 for all brain tumors, astrocytomas, and meningiomas, respectively. Parental endometrial cancer and melanoma were associated with offspring astrocytoma, and parental breast and thyroid cancers with offspring ependymoma and neurinoma, respectively. SIR for sibling nervous system tumors from brain tumor probands was not increased overall but was 2.5 in those diagnosed at ages 15-34 years. CONCLUSION: These data show a familial risk for brain tumors among adults.