In 1970, before the implementation of strict controls on emissions in motor vehicle exhaust gas (MVEG), the annual U.S. incidence of fatal accidents by carbon monoxide in the MVEG was ∼800 and that of suicides ∼2000 (somewhat less than 10% of total suicides). In 1987, there were ∼400 fatal accidents and ∼2700 suicides by MVEG. Accounting for the growth in population and vehicle registration, the yearly lives saved in accidents by MVEG were ∼1200 in 1987 and avoided suicides ∼1400. The decrease in accidents continues unabated while the decrease in expected suicides by MVEG reached a plateau in 1981-1983. The reasons for this disparity are discussed. Juxtaposition of these results with the projected, but statistically undetectable, cancer risk avoidance of less than 500 annually in 2005 (as compared to 1986) associated with the abatement of ambient MVEG pollutants, plainly shows that, in terms of mortality, the unanticipated benefits of emission control far overshadow the intended benefits. With the spread of MVEG controls these benefits will accrue worldwide.