Among all Swedish men, 20 to 64 years of age and employed in 1960, railway workers were selected and compared with the population at large, concerning the incidence of leukemia, lymphoma, tumors of the brain, breast, and the pituitary gland. The study was a re-analysis of the 1961-79 incidence data previously showing no increase in risk for leukemia and brain tumors for railway workers. In the present study, follow-up was divided into two 10-year periods, and elevated relative risks (RR) were found for the first decade. For the first decade, engine drivers and conductors combined had an RR of chronic lymphocytic leukemia, acute myeloid leukemia, and lymphoma of 1.9 (95 percent confidence interval [CI] = 0.9-4.0), 1.4 (CI = 0.4-4.3), and 1.0 (CI = 0.5-1.9), respectively. For all brain tumors, the RR was 1.2 (CI = 0.8-1.9), with a higher risk estimate for those below age 30 (RR = 12.2, CI = 2.8-52.5). Three cases of breast cancer and nine cases of tumors of the pituitary gland occurred among engine drivers and conductors, corresponding to RRs of 4.9 (CI = 1.6-11.8) and 3.2 (CI = 1.6-6.2), respectively. Work on trains entails extremely high exposure to low frequency magnetic fields (EMF). The results give some support to the hypothesis of an association between EMF and certain types of cancers. The outcome for the pituitary gland, being a focal point of hormonal regulation, suggests a hormonal link.