Survival of human poliovirus type 1 in a sandy loam soil appeared to be deleteriously influenced by aerobic microorganisms. The effect was determined by comparing the survival of virus in soil under four different possible combinations of aerobic versus anaerobic (H2-CO2) atmosphere and sterile versus nonsterile condition. Storage of samples was done in humid chambers to prevent soil desiccation. The effect attributed to aerobic microorganisms was measurable and statistically significant at all three incubation temperatures used in the study (1, 23, and 37 degrees C), with the increase in inactivation rate attributable to aerobic microorganisms generally being two to threefold. No comparable effect was observed to occur for anaerobic microorganisms under the sets of conditions employed in the study.