In this review, we aim to bring together major trends in autism research at three levels: biology, behaviour and cognition. We propose that cognitive theories are vital in neuropsychology, which seeks to make connections between brain abnormality and behavioural symptoms. Research at each of the three levels is incomplete, but important advances have been made. At the biological level, there is strong evidence for genetic factors, although the mechanism is, as yet, unknown. At the behavioural level, diagnosis and education are becoming more coherent and less controversial, sometimes been missing in the field. Clinical work on autism has often ignored theories of normal development, neuropsychological accounts have tended to focus narrowly on single symptoms at the cost of the full clinical picture, and psychological accounts have frequently ignored biological research. Our review attempts to integrate some of this considerable body of work in order to examine possible neuropsychological conceptions of autism. We have not attempted to be exhaustive in our discussion of current work, and instead refer the reader to recent reviews of each area covered, as well as a comprehensive field review by Bailey et al. (1996).