BACKGROUND: Empirical evidence for the validity of the diagnostic label disintegrative psychosis is sparse. The issue of whether it is a separate form of infantile autism is unresolved. METHOD: To investigate the validity of disintegrative psychosis as defined in ICD-9, the natural history of 13 cases were compared with 39 matched cases of infantile autism on various outcome variables. Average follow-up time was 22 (11-33) years. RESULTS: Statistically significant differences were found between the two groups in terms of number of admissions to non-psychiatric departments, occurrence of comorbid epilepsy, social style, and score on the Global Assessment of Functioning scale. In most other areas assessed there was a tendency, although statistically insignificant, towards a better outcome in the infantile autism comparison group. CONCLUSIONS: Our findings provide some support for maintaining a diagnostic category of disintegrative psychosis as distinct from infantile autism.