This study reports on the pharmacokinetics of the elimination of the metabolites of three toxic organophosphorus compounds (soman, sarin and GF). Urine, blood and lung tissue were collected from rats dosed subcutaneously at 75 pg kg-'. Urinary excretion of the metabolite was the major elimination route for these three compounds. The major differences among them were primarily the extent and rate of excretion. The hydrolyzed form, alkylmethylphosphonic acid, was the single major metabolite formed and excreted in urine by a non-saturable mechanism. Nearly total recoveries of the given doses for sarin and GF in metabolite form were obtained from the urine. The terminal elimination half-lives in urine were 3.7 ? 0.1 and 9.9 2 0.8 h for sarin and GF, respectively. Soman metabolite showed a biphasic elimination curve with terminal half-lives of 18.5 t 2.7 and 3.6 ? 2.2 h. Soman was excreted at a slower rate with a recovery of only 62%. Lung was the major organ of accumulation for soman. In blood the toxic agents were concentrated more in red blood cells than in plasma. The acid metabolites can serve as a better chemical marker for monitoring organophosphorus exposure in humans via their higher concentration and longer half-life in urine than the parent compounds. CCC 0260-437)(/94/030 19545 0 1994 by John Wiley & Sons, Ltd.