A case-referent study assessed the association of medically certified sick leave from work with some occupational characteristics: hospital, care unit, and two work-load indices (patients' average length-of-stay, and nurse-patient ratio). Study participants were nurses from seven general hospitals in Quebec City, who had been employed for at least 6 months at the time of study. Cases (n = 1165) experienced at least one episode of medically certified sick leave between January 1, 1984 and May 31, 1987. Referents (n = 1165) were chosen from subjects who had no such leave and were matched to cases on the basis of dates on which sick leave occurred. Occupational data were collected from employment records and administrative files. Analysis was conducted using multiple logistic regression. Statistically significant associations were found between sick leave and one hospital, two care units, and nurse-patient ratio among head nurses. These odds ratios were independent of length of service in the hospital or in the actual job assignment. The study supports the pertinence of using certified sick leave as a nonspecific indicator of health outcomes.