Rats will initiate self-administration of d-amphetamine and achieve a stable injection rate within 7-10 days. Animals injected intraventricularly with 5,7-dihydroxytryptamine, which selectively destroys 5-hydroxytryptamine-containing neurons, consistently self-injected larger amounts of d-amphetamine from the first day of training, but the acquisition of a stable rate of drug self-administration was not altered. Bilateral microinjection of 5,7-dihydroxytryptamine into nucleus accumbens failed to alter either the acquisition of d-amphetamine self-administration or the maintenance of a stable rate of injection.