Pervasive Developmental Disorders is a category of disorders that includes autism and related conditions. While these disorders are rare, they represent a significant public health problem because they are extremely debilitating and lack efficacious therapies. Neuroleptic use in PDD is high and the population appears to be at increased risk of serious sequelae including tardive dyskinesia. Newer atypical neuroleptics including risperidone are now used in 87% of cases but dosing, safety and efficacy is undetermined in the vulnerable population.