The experiment was designed to compare triadimefon to known psychomotor stimulants. Four rats were trained to perform under a mult FI 1-min FI 5-min schedule of milk reinforcement. They then received a series of dosages of triadimefon (10-170 mg/kg, i.p.) and of methylphenidate (1-17.3 mg/kg, i.p.) in a counterbalanced order. Certain dosages of triadimefon increased response rates for all rats in the FI 1-min component and in the FI 5-min component. Methylphenidate increased response rates in each component for only two rats. Temporal patterns of responding were disrupted more in the FI 5-min component than in the FI 1-min component by both triadimefon and methylphenidate. Performances were then evaluated following a series of dosages of d-amphetamine (0.3-3.0 mg/kg, i.p.) and chlorpromazine (0.5-2.0 mg/kg, i.p.). Response rates in FI 1-min were increased by d-amphetamine for three rats and in FI 5-min for two rats. d-Amphetamine, like triadimefon and methylphenidate, produced a greater disruption of response patterning in FI 5-min than in FI 1-min. Chlorpromazine only decreased response rates, but also produced some disruption in FI 5-min response patterning.