The responses obtained with drugs that act at dopamine receptors depend on the spectrum of receptors stimulated, the pattern of stimulation and the neuronal signal-transduction pathways that are activated. In the absence of drugs that reliably discriminate between the various cloned receptors, elucidating the role of these receptors has largely relied on molecular genetic approaches that include expression of genes for receptors in cell lines and manipulation of this expression in animal models. Connecting molecular events that occur consequent to receptor stimulation with the resulting physiological effects entails bridging a complex network of interactions. This article reviews the current understanding of the molecular, cellular and systemic consequences of activation of the different dopamine receptors.