A series of 122 patients with colorectal carcinoma belonging to 22 verified Finnish cancer family syndrome kindreds was examined retrospectively. The identification of this hereditary syndrome and the best lines of management were the main concerns of this study. Early presentation (mean, 41 years), the proximal location of the colonic tumors (54 percent in the right colon) and the high frequency of multiplicity (24 percent) were demonstrated clearly. In only 40 percent of patients, however, was a positive family history demonstrable with certainty at the time of diagnosis of the colorectal tumor. A high tendency of second and third colorectal carcinomas to occur was observed with mean annual cumulative rates of 3.2 and 5.4 percent, respectively. It was concluded that identification of the cancer family syndrome remains problematic; for example, with regard to the planning of screening procedures for asymptomatic relatives; until the family history has been clarified carefully. A verified case of colorectal cancer in a cancer family syndrome kindred requires lifelong follow-up examinations of the remaining colon and rectum. Abdominal colectomy is the operation of choice.