A major goal of psychology is to understand the underlying organization of cognition-that is, to develop formal accounts of cognitive processes, inforн mation flow, and representations. Ultimately, one wants to understand cogniн tion not just as an abstraction, or in terms that are simply plausible or internally consistent. Rather, one wants to know as specifically and concretely as possiн ble how the job is actually done. It is often said, working from logical considн erations alone, that in describing the function of a complex device one can separate consideration of its formal operations (the software) from considerн ation of the mechanisms used to implement the operations (the hardware). In the history of cognitive psychology it has been traditional to separate psychoн logical theory from neurobiological detail. Until recently, this approach could be justified by the fact that relevant neurobiological information was simply not available. Yet it is increasingly true that the domains of psychology and neuroscience are reinforcing each other and working hand in hand (Kandel & Squire 1992). Neuroscience has become relevant and useful for elucidating the structure and organization of cognition. Here we consider recent work on learning and memory from a combined psychology-neuroscience point of view. We focus on the characteristics of various forms of memory, their relationship to each other, and how they are organized in the brain. Although work with normal human subjects has been vital to this line of inquiry, our discussion draws especially on neuн ropsychological studies of memory-impaired patients and related studies with experimental animals. For recent reviews that emphasize work with normal subjects, see Hintzman (1990), Richardson-Klavehn & Bjork (1988), Schacter et al (1993), and Tulving (1991).