The risk of specific histologic types of leukemia among farmers was investigated using mortality records from Nebraska for the years 1957-1974. The frequency of farming as an occupation listed on the death certificates among 1,084 leukemia deaths was compared to the corresponding frequency for 2,168 controls for calculation of odds ratios (OR). The elevated OR for chronic lymphatic leukemia among farmers was statistically significant (OR = 1.67), while elevated ORs for acute lymphatic leukemia (OR = 1.34), acute monocytic leukemia (OR = 1.94), and acute unspecified leukemia (OR = 2.36) were not. Farmers who died at younger ages or who were born in more recent years were at greater risk of acute lymphatic, acute myeloid, chronic myeloid, acute unspecified, and unspecified leukemia than other farmers. Certain cell types were related to agricultural characteristics of the subject's county of residence, although few were statistically significant. Farmers from counties with large cattle inventories and significant dairy activity were at higher risk of chronic lymphatic leukemia. Farmers from major corn-producing, hog- and chicken-raising, and pesticide- and fertilizer-using counties tended to be at higher risk of acute lymphatic, acute myeloid, chronic myeloid, and acute unspecified leukemia than farmers from counties less involved in the production or use of these agricultural factors.