The acute effects of single subtoxic doses (1/48-1/9 of LD50) of two potent organophosphates (OPs), sarin (12.5 and 50 micrograms/kg i.p.) and soman (4 and 20 micrograms/kg i.p.), were studied on behavior, motor performance and nociception in male Wistar rats. On the elevated plus-maze with two open + two closed arms, higher doses of soman and sarin decreased the proportion of entries made onto open arms (p less than 0.05), while the total number of entries onto open + closed arms was unchanged. On the narrow elevated horizontal bridge, the latencies to reach the safe platform were prolonged with the higher dose of sarin (p less than 0.05) but not with that of soman. On the broad and rod bridges, the latencies of OP-treated rats did not differ significantly from those of controls. OPs did not significantly impair either learning frequency in one-trial passive avoidance test, rotarod performance or nociception in hot plate test. The results suggest that in acutely nontoxic doses sarin and soman affect the behavior of rats, and that the action profiles of the OPs differ from each other. Both soman and sarin change the behavior of rats in the plus-maze test but only sarin seems likely to impair motor coordination/balance.