There is evidence to suggest that genetic factors play an important role in the development of basal cell carcinomas (BCCs), and that skin neoplasms might be a sign for a genetic predisposition to cancer. We investigated whether the incidence of visceral and skin malignancies among first-degree relatives of BCC-patients was increased. Postal questionnaires were sent to 249 BCC-patients, who were divided into two groups (young = BCC under the age of 51 years and older = BCC over the age of 50 years), and asked them about cancer in their first-degree relatives. The reported numbers of cancer among the relatives were compared with the expected numbers based on sex and age-specific population-based incidence rates. The accuracy of the reported diagnoses was verified. A total of 157 BCC-patients reported 277 malignancies in 1,272 relatives. The incidence of the following cancers was higher than expected in relatives from young BCC-patients: bone and soft tissue (O/E = 3.91; 95% CI: 1.43-8.66), skin (O/E = 2.13; 95% CI: 1.30-3.29) and digestive tract (O/E = 1.59; 95% CI: 1.10-2.23). In relatives of older BCC-patients, only the incidence of digestive tract cancer was higher than expected (O/E = 1.44; 95% CI: 1.08-1.89). Diagnoses that were verified turned out to be accurate in 87% of the cases. This study suggests that the risk of certain cancers, particularly that of the digestive tract, in first-degree relatives of BCC-patients is increased. These findings may indicate a genetic predisposition to both skin and visceral malignancies in this patient group.