In 1974, Professor Muzaffer Aksoy established a link to leukemia in humans as a result of occupational exposure to benzene. The aim of this study is to evaluate his epidemiological approach for his investigation on the effects of benzene and to bring attention to the benzene problem in Turkey. Dr. Aksoy observed that a large group of leukemic patients were shoemakers, or they worked in leather manufacturing. In the 1960s, benzene was a popular solvent in the leather industry. Dr. Aksoy conducted a field investigation in Gedikpasa-Istanbul, where the shoemakers worked so that he could draw his key observations from actual environmental conditions. With a gas detector, he found the concentration of benzene in these work places to be 150-210 ppm and up to 650 ppm on rare occasions. He performed an epidemiological study and health education among 28,500 shoe, slipper and handbag workers during the period from 1967 to 1974. He published these data, establishing an association between benzene and leukemia. The incidence of leukemia among the shoe workers was decreased by screening, health education, and legislative actions in Turkey, but it began to increase again because of lack of an occupational health policy and underestimation of the problem. These results suggest the importance of primary prevention of occupational cancers. Dr. Aksoy's epidemiologic approach may highlight the necessity for detailed investigations of the occupational status of patients who need medical aid in order to diagnose the real underlying factor.