The disposition of (14)C-labeled pentachloronitrobenzene (PCNB), two of its analogues pentachlorophenol (PCP) and hexachlorobenzene (HCB), and captan was examined as seed-protectant coatings in a terrestrial microcosm chamber (TMC) in comparison to a reference compound, dieldrin (HEOD). The TMC contained a synthetic soil medium, agricultural crops, numerous invertebrates, and a gravid gray-tailed vole (Microtus canicaudus). Captan and PCP degraded more rapidly in soil and plants than did PCNB, which was degraded somewhat more quickly than HCB and HEOD. By 45 days post-planting, total soil residues (parent + metabolites + bound residues) had declined from a nominal 3 ppm to about 1 ppm for all chemicals but captan (0.26 ppm), while parent residues become undetectable for PCP and captan. Residues in invertebrates and the vole were low for all chemicals, but HCB and HEOD showed ecological magnification indices (EMs) in the vole of 17.7 and 2.1 respectively, as compared to 1.2 for PCNB. None of the chemicals adversely affected vole survival, although the PCNB-exposed vole had no surviving pups. Only HEOD greatly decreased cricket survival.