History of cigarette smoking and risk of leukemia and myeloma: results from the Adventist health study. The risks of leukemia and myeloma associated with cigarette smoking were evaluated in a cohort study of 34,000 Seventh-day Adventists. Although Seventh-day Adventists do not smoke by church proscription, many are adult converts who smoked cigarettes prior to their baptism into the church. In comparison with those who never smoked, ex-smokers experience a relative risk of 2.00 (95% confidence interval = 1.01-3.95) for leukemia and 3.01 (95% confidence interval = 1.13-8.05) for myeloma. Risks increased in a dose-response fashion with increasing numbers of cigarettes smoked daily for both leukemia (trend P = .009) and myeloma (trend P = .005). Also, the risks of both leukemia and myeloma increased with the total duration of cigarette smoking. The cigarette smoking-leukemia relationship was strongest for myeloid leukemia, for which ex-smokers experienced a relative risk of 2.24 (95% confidence interval = 0.91-5.53). These data lend support to the hypothesis that cigarette smoke may induce malignant degeneration in bone marrow and its products. 