The effect of exhaust emissions, including carbon-monoxide (630080) (CO), on motor vehicle examiners was investigated. Mortality rates among 1,558 examiners employed for at least 6 months between 1944 and 1973 were determined from local records. CO readings were taken at 31 of 38 inspection stations and 27 examiners were administered carboxyhemoglobin (COHb) tests. The mean CO concentrations for indoor and outdoor inspection stations were 24.4 and 10.0 parts per million, respectively. The mean pre and post shift COHb concentrations were 3.3 and 4.7 percent, respectively. There were 237 deaths from all causes during the period of study, as opposed to an expected 260.4 deaths. Among the examiners, there were 124 deaths from cardiovascular diseases compared to 118.4 expected, and 52 deaths from malignant neoplasms compared to 47.8 expected. There were fewer deaths than expected from diseases of the nervous system, nonmalignant diseases of the respiratory and digestive systems, and accidents. The authors suggest that the excess of deaths due to cardiovascular diseases is due to CO exposure. The excess cancer death rate may be due to contaminants other than CO.