Twenty-four Finnish families with 2 or more glioma patients were identified through questionnaires sent to 369 consecutive glioma patients receiving surgery at Tampere University Hospital during 1983-94. To explore whether unusual cancer susceptibility is involved, the cancer risk of 2,664 family members was estimated using population-based data from the Finnish Cancer Registry. Among the total cohort of relatives, 88 cancers were observed during 1953-97. The overall cancer risk among 12 families with juvenile onset gliomas was significantly decreased (standardized incidence ratio [SIR] 0.6, 95% confidence interval [CI]: 0.4-0.9). Among 12 families with adult onset gliomas, the overall cancer risk was equal to that of the reference population (SIR 1.1, 95% CI: 0.8-1.4) whereas the risk of skin melanoma (SIR 4.0, 95% CI: 1.5-8.8) and meningioma (SIR 5.5, 95% CI: 1.1-16) were significantly increased. Several other tumors, including those associated with neurofibromatosis 1 and 2, tuberous sclerosis and Li-Fraumeni and Turcot syndromes were surveyed, but no elevated risks were observed. In conclusion, the presence of meningiomas and skin melanomas in glioma families may indicate a novel association as a cancer susceptibility trait.