Over a 1 1/2-year period a cluster of 5 patients demonstrated similar characteristics of large bowel cancer, in terms of histological type, occupation in the same manufacturing unit of a carpet factory, sex, young age (less than 50), and a negative familial history of cancer. Therefore, the lifetime occupational familial history of all known cases of colorectal cancer, occurring between 1965 and 1975 in the geographic region where the factory was situated, were reviewed to compare the incidence, histopathological type, and the site distribution of colorectal cancer in the exposed and in a control group. Of 1000 subjects with large bowel cancer so far analyzed 30 have had a positive occupational exposure. A detailed analysis of 12 cases occurring from 1971 to 1975 indicates that the observed age and sex-adjusted relative risk ratio was 10 timer higher among workers in the carpet factory than among other industrial workers. The observed morbidity in the studied group was 11.4 times higher than the expected one.