This paper presents a review of past and current research on the diagnosis of Asperger syndrome (AS) in children. It is suggested that the widely used criteria for diagnosing AS in the "Diagnostic and Statistical Manual of Mental Disorders" (DSM)-IV are insufficient and invalid for a reliable diagnosis of AS. In addition, when these diagnostic criteria are applied, there is the potential bias of receiving a diagnosis towards the high-functioning end of the autism spectrum. Through a critical review of 69 research studies carried out between 1981 and 2010, this paper shows that six possible criteria for diagnosing AS (specifically, the age at which signs and symptoms related to autism become apparent, language and social communication abilities, intellectual abilities, motor or movement skills, repetitive patterns of behaviour and the nature of social interaction) overlap with the criteria for diagnosing autism. However, there is a possibility that some finer differences exist in the nature of social interaction, motor skills and speech patterns between groups with a diagnosis of AS and autism. These findings are proposed to be of relevance for designing intervention studies aimed at the treatment of specific symptoms in people with an autism spectrum disorder. (Contains 6 tables.)