This report presents the results of proportionate mortality ratios (PMR) and proportionate cancer mortality ratios (PCMR) among 15,843 members of the International Union of Operating Engineers who had died between 1988-1993. Operating engineers represent one of the 15 unions in the Building and Construction Trades Department and are responsible for the operation and maintenance of heavy earthmoving equipment used in the construction of buildings, bridges, roads, and other facilities. Using U.S. proportionate cancer mortality as the referent, statistically significant elevated mortality was observed for cancers of the lung (PCMR = 1.14, 95% confidence interval (CI) = 1.09-1.19) and bone (PCMR = 2.14, CI = 1.19-3.52). Using U.S. proportionate mortality as the referent, statistically significant elevated mortality was observed for other benign and unspecified neoplasms (PMR = 1.54, CI = 1.09-2.13), emphysema (PMR = 1.37, CI = 1.20-1.55), other injuries (PMR = 1.43, CI = 1.20-1.70) (which included crushing under/in machinery, tractor rollover, run over by crane), and suicide (PMR = 1.22, CI = 1.06-1.40). The PMR for leukemia, and aleukemia (PMR = 1.19, CI = 1.02-1.37), but not the PCMR (1.07, CI = 0.92-1.24), was also significantly elevated. Some of the occupational exposures that may have contributed to these excesses include diesel exhaust, asphalt and welding fumes, silica dust, ionizing radiation, and coal tar pitch. The present study underscores the need to control airborne exposures to these substances and for injury prevention efforts aimed at operating engineers in the construction industry.