The morbidity of oil shale workers (SIC-1311) was investigated. A total of 325 workers involved in the mining, retorting, maintenance, or supervisory aspects of oil shale production were examined during 1978 and 1979; 323 Utah coal miners served as comparisons. The subjects were questioned as to respiratory disorders, chronological occupational, smoking, and general medical histories, after which they underwent dermatologic examinations. Sputum for cytology was collected. Chi square tests and t-tests were used to compare responses and characteristics between groups; a logistic regression model served to relate oil shale work plus sun exposure and smoking to the presence or absence of skin, urine, and lung abnormalities. The prevalence of respiratory symptoms was similar to or less than that of the comparisons in all categories and did not significantly increase with length of service or smoking history. Oil shale workers exhibited a 21 percent incidence of removed skin tumors, including multiple removals, as opposed to 11 percent of the comparisons. Actinic keratoses were 6 percent more prevalent in the oil shale group than in the comparisons. Cytology revealed a significant association between metaplasia and oil shale production. Oil shale workers also had significantly more moderately and markedly atypical findings on urine cytology. The authors conclude that there is a correlation between shale oil exposure and the premalignant lesion of actinic keratosis. They recommend that close attention be given to the skin, the respiratory system and urinary system during medical surveillance of oil shale workers.