Measurements were made of the bioavailability of mutagens with a bacterial genotoxicity assay specifically designed for use with the solid phase of soil. Short-term sorption of benzo(a)pyrene, 7,12-dimethylbenz(a)anthracene, 9-phenylanthracene, captan, and aldicarb by six markedly different soils resulted in a 28.2 to >99% decline in availability for genotoxicity. This reduced bioavailability varied markedly with the soil and the compound. The reduced genotoxicity was not a result of the destruction of the compounds since, with few exceptions, >90% of each compound was recovered by Soxhlet extraction. The bioavailability of captan was correlated with surface area and organic C content, but the availability of the other mutagens was not correlated with other properties of the six soils. However, if soils with <0.7% organic matter were not considered, correlations were evident between organic C content and the bioavailability of the three polycyclic aromatic hydrocarbons (r values of 0.90 or higher) and ald...