The present study examined the discriminative stimulus properties of amphetamine (AMP) at progressively lower doses in lead-exposed and normal rats. In addition, generalization gradients of AMP, apomorphine, methylphenidate, and caffeine to both high and low training doses of AMP were determined in these rats. Under the high AMP training dose condition (1.0 mg/kg, IP) generalization gradients of AMP were similar for lead-exposed and control rats. When the training doses were progressively lowered, the lead-exposed rats tended to require a higher range of AMP doses (0.24-0.49 mg/kg) than did control rats (0.18-0.32 mg/kg) to maintain discriminative control. In parallel with this, the minimal discriminable doses tended to be higher for lead-exposed rats than for control rats. Methylphenidate generalization gradients were different for lead-exposed and control rats under the high AMP training condition but became similar under the low AMP training condition. No differences attributable to training dose or lead exposure were evident for apomorphine or caffeine.