Abstract 1. 1. This review considers the evidence for specific dopamine receptors in the mammalian peripheral vascular system, the mammalian central nervous system, and in the brain of Helix aspera. 2. 2. From the evidence of structure-activity studies on dog kidney and snail brain it seems that dopamine receptors show a higher degree of specificity for agonists than do α or β receptors. 3. 3. It is possible to block some of the action dopamine in the mammalian system with the compounds haloperidol and chlorpromazine. However, these substances have no direct dopamine-blocking activity on neurons of Helix. 4. 4. In the brain of Helix some neurons are inhibited compounds with dopamine-like activity and are excited by 5-hydroxytryptamine (5-HT). The lysergic acid derivatives, ergometrine, methysergide, and lysergic acid diethylamide, are antagonists of both 5-HT and dopamine on these cells, whereas cyproheptadine blocks the action of 5-HT but does not affect the dopamine response. 5. 5. On the basis of these and other results a model composite dopamine/5-HT receptor has been proposed. 6. 6. Suggestions are made regarding chemicals which should bind to the proposed receptor.