In view of the immense amounts of combustion waste products spewed annually into the atmosphere by automobiles, this investigation seeks to answer whether or not such exhausts have deleterious effects on the productivity rates and processes of natural areas. We ask specifically, what is the influence of car exhaust on the meiofaunal and macrofaunal invertebrates of the forest litter. Previous research on this same topic by one of us showed a decrease in both the number and kinds of organisms in litter after exposure to car exhaust and water in a woodland. ... We found no evidence for regularly-occurring deleterious effects on either numbers or kinds of organisms from the exhaust applied in this study. In fact, there is some suggestion that the exhaust may exert a stimulatory influence on numbers and kinds. Subsequent studies on exhaust influence upon metabolic rates, on reproductive and nutritional success and on separate life history stages of litter organisms are needed to explore this possibility. The exhaust materials responsible for the deleterious effects seen in the earlier study apparently did not occur in a high enough concentration to exert a lethal influence on the organisms in this study. The better mechanical condition of the motor and its pollution control device probably made the difference.