This paper presents results from a retrospective cohort study of workers of a synthetic textiles plant in Quebec. This plant has been the subject of a previous case-control study, in which an excess risk of colorectal cancer was observed. The cohort consisted of 7,487 men and 2,724 women who had worked at least 1 year at the plant and who were either working in 1947 or were newly employed between 1947 and 1977. The period of follow-up was from 1947 to 1986, thus yielding 307,278 person-years of observation. Mortality rates for most causes of death were less than expected; the standardized mortality ratio (SMR) for all causes of death among men was 0.73 (95% confidence interval (CI): 0.70-0.77) and among women it was 0.77 (95% CI: 0.68-0.87). For men, the SMR for all neoplasms was 0.76 (95% CI: 0.69-0.83) and for colorectal cancer it was 0.69 (95% CI: 0.52-0.92). For women, the SMR for all neoplasms was 1.01 (95% CI: 0.83-1.22) and for colorectal cancer it was 1.02 (95% CI: 0.57-1.69). Among men, risks for ischemic heart disease increased with increasing length of service at the plant, even though the SMRs were less than unity (overall SMR = 0.76; 95% CI: 0.70-0.83); no trend was observed for women. SMRs and relative risks were also calculated according to duration of employment in each processing unit. Of the scores of associations tested, very few showed increased risks. Of those showing increased risks, the data were not persuasive in indicating a connection with work at the plant; nevertheless, some of these associations may be worth following up in future studies. The following associations of potential significance were observed: all cancers, liver and gallbladder cancers, non-Hodgkin's lymphomas, and reticulum cell sarcoma in the cellulose acetate fiber manufacturing unit; all cancers in the polypropylene and cellulose triacetate extrusion unit and in the janitor unit; leukemias in the unexposed unit; ischemic heart disease in the maintenance and janitor units; and cerebrovascular disease in the weaving unit.