This article examines the diagnosis of autism as it has been presented in the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM) and is expected to be presented in the next revision of the DSM. Then I look at the relationship of autism and other labels and conditions, including Asperger's disorder, sensory processing disorder, social communication disorder, mental retardation, social anxiety, obsessive-compulsive disorder, narcissistic disorder of childhood, and psychosis. I consider how to describe these relationships, looking at concepts of co-morbidity, overlapping borders, a range of functioning, and changes over time due to therapy, maturation, and other influences. Two vignettes illustrate these ideas.