A family history of colorectal cancer is a known risk factor for the disease. As a result of different study designs from different populations, the strength of this association varies in the literature. We intended to define the incidence and the risk predictors in first-degree relatives of patients with colorectal cancer in the Austrian population. A family history was obtained from first-degree relatives of 100 consecutive patients with sporadic colorectal cancer. Life-table methods were used to compare the observed and expected incidence of colorectal cancer and the influence of differences in risk for first-degree family members. The calculated lifetime risk for colorectal cancer in Austria is 1:16. Individuals with a positive family history had a 4.6-fold risk (p </= 0.0001), particularly in the case of a young index patient (p </= 0.011) or if two or more family members were affected (p </= 0. 001). In addition, the risk for gastric cancer in relatives was increased almost fourfold (p </= 0.0001). We have confirmed for Austria that a positive family history of colorectal cancer is a strong risk factor, and that this risk is comparable to that in other Western countries. We have shown that relatives are also at increased risk for gastric cancer.