The prevalence of childhood disintegrative disorder (CDD) is unknown. In this study, 32 epidemiological surveys of autism and pervasive developmental disorders published in English language journals since 1966 were reviewed. Four surveys yielded estimates for CDD ranging from 1.1 to 6.4 per 100,000 subjects. A pooled estimate across these four surveys is 1.7 per 100,000 (95 percent Confidence Interval: 0.6-3.8 per 100,000). The conclusion is that CDD is very rare and its prevalence is 60 times less than that for autistic disorder, assuming a prevalence of 10 per 10,000 for autism. If a rate of 30 per 10,000 is taken for all PDDs, only one child out of 175 children with a PDD diagnosis would, on average, meet criteria for CDD.