Chronic administration of drugs which interfere with normal neurotransmission within animal nervous tissue (e.g. neurotransmitter receptor antagonists) is known to result in the development of behavioral supersensitivity. During recent years, evidence has been presented which indicates that neurotransmitter receptor agonists also produce behavioral supersensitivity. This study shows that, using stereotypic cage-climbing behavior in mice, chronic administration of apomorphine, and N-n-propylnorapomorphine (two direct-acting dopamine agonists) and d-amphetamine (an indirect dopamine agonist) produced an enhanced behavioral response to a test dose of apomorphine 4, 8 and 12 days after cessation of chronic drug injections.