A study of hematopoietic cancer mortality among motor vehicle mechanics in Washington, DC was conducted to due to the occurrence of three cases of leukemia (index cases) among motor vehicle mechanics working for the DC government. The cohort was composed of 338 males employed as automobile or mobile equipment mechanics by the DC Department of Public Works for at least 1 year between January 1977 and December 1989. The vital status of the cohort was determined on December 1991. Death certificates were obtained for the decedents and reviewed. Standardized mortality ratios (SMRs) were computed using mortality rates of the general DC population as a reference. Associations between the SMRs and estimated occupational exposures to fuels and solvents (categorized as high, medium, or low) were also examined. Thirty three deaths occurred in the cohort during the study period, which represented a significantly decreased risk, SMR 0.50. Mortality from all cancers was also decreased, SMR 0.55. Three deaths classified as being from lymphatic and hematopoietic cancer, including one index case, occurred. These yielded an SMR of 3.63, a nonsignificant increase. All three deaths occurred in the high exposure group. For this group, which included 297 subjects, the SMR was 4.22, also nonsignificant. Of the three deaths, two were from leukemia and aleukemia, which represented a significantly increased risk with an SMR of 9.26. The third death was from other neoplasms of lymphatic and hematopoietic tissues, which yielded a nonsignificantly elevated risk, SMR 2.57. The remaining two index cases were still alive at the time of the study. One died in 1992 after the study ended. The authors conclude that excess mortality from hematopoietic cancers has been detected in this group of motor vehicle mechanics. This finding supports the results of previous studies which found that motor vehicle mechanics, probably because of their exposure to gasoline, are at increased risk for hematopoietic malignancies.