Two male children meeting criteria for Childhood Onset Pervasive Developmental Disorder (COPDD) are described. The current DSM-III category of COPDD may have value in separating these children from others with PDD. The authors suggest that these two children, and other children described in the literature as having dementia infantalis and/or disintegrative psychosis, have a distintegrative disorder resulting in muteness, profound mental retardation and severe autistic symptomatology. The term "pervasive disintegrative disorder" may be appropriate for such children and specific diagnostic criteria are suggested. The disorder appears to be extremely rare, with a prevalence estimate of 0.11 per 10,000.