General anesthetic agents are unique in clinical medicine, because they are the only drugs used to produce unconsciousness as a therapeutic goal. In contrast to older hypotheses that assumed all general anesthetics produce their central nervous system effects through a common mechanism, we outline evidence that general anesthesia represents a number of distinct pharmacological effects that are likely mediated by different neural circuits, and perhaps via different molecular targets. Within the context of this neurobiological framework, we review recent molecular pharmacological and transgenic animal studies. These studies reveal that different groups of general anesthetics, which can be discerned based on their clinical features, produce unconsciousness via distinct molecular targets and therefore via distinct mechanisms. We further postulate that different types of general anesthetics selectively disrupt different critical steps (perhaps in different neuronal circuits) in the processing of sensory information and memory that results in consciousness.