The disposition of 14C-labeled methylparathion, parathion, and p-nitrophenol applied as a foliar spray was examined in the Terrestrial Microcosm Chamber (TMC) and compared to a reference compound, dieldrin. The impact of soil type (synthetic vs natural) and airflow rates through the camber on methylparathion disposition were evaluated. The TMC contained either a synthetic soil medium or Willamette sandy loam soil plus agricultural crops, numerous invertebrates, and a gravid gray-tailed vole (Microtus canicaudus). Dieldrin was accumulated to a lesser extent than any of the organophosphates in the synthetic soil. Concentrations of methylparathion in the upper layer of Willamette sandy loam soil were consistently lower than those observed with the synthetic medium. Increased airflows altered methylparathion distribution primarily through increased export from the TMC. Although recovery of dieldrin was lower than with equivalent applications of organophosphates, a significantly greater concentration was detected in the vole. Only dieldrin appeared to affect vole survival.