The acute effects of single oral doses, 0.4 and 2.0 mg/kg, of trichothecene T-2 mycotoxin on behaviour, motor performance and nociception were studied in male Wistar rats. Both doses are sublethal and did not cause overt acute signs of intoxication. In the open field test, 2.0 mg/kg of T-2 toxin increased motionlessness and decreased sniffing (P less than 0.05) 4 hr after the administration. The higher dose shortened step-through latencies in the test trial of the 24-hr passive avoidance test (two-way shuttle box). The exponential data analysis showed that, in those rats that did not learn to avoid the dark (unsafe) compartment of the box, the retention after 2.0 mg/kg of T-2 toxin was only 25% of that in controls (P less than 0.001). T-2 toxin had no effect on motor coordination in the rotarod test and in the bridge walking test 7-8 hr after administration. T-2 toxin had no effect on nociception in the hot place test 8.5 hr after administration. The results suggest that T-2 toxin has some inactivating effects on behaviour of rats, and it seems to cause an impairment in the passive avoidance test at dose 2.0 mg/kg.