OBJECTIVES: A number of medication surveys conducted in the U.S. have demonstrated a high level of psychotropic drug use in patients diagnosed with pervasive development disorder (PDD).  Medication use is of interest as not many products are approved for treatment in autism. Describe drug use in subjects newly diagnosed with PDD in Quebec province. METHODS: A cohort study was built by using Quebec RAMQ and Med-Echo databases for subjects having a new PDD diagnosis (ICD-9 codes: 299.0-299.9) between January 1998 and December 2010.  Cohort entry date was the date of a first diagnosis confirmed by the absence of PDD diagnosis in previous 2 years, and aged less than 26 years.  Descriptive analyses of patient characteristics were done at cohort entry and drug use profiles were done the year prior to, and within the 3 years following diagnosis. RESULTS: A cohort of 4,684 subjects was identified; 78% of patients were male and the age ranges were as follows: 41.9% (1-5 years), 31.2% (6-12 years), 12.3% (13-17 years), 14.7% (18-25 years). Prior to being diagnosed with PDD, 35% received at least 1 psychoactive drug.  Methylphenidate was most common in 6-12 year olds (36%) whereas antipsychotics were most common in the 13-17 group (28.6%) and in the adult population (51.7%). Antipsychotic use was also present in younger children: 5.7% in 1-5 year olds and 23% in 6-12 year olds, 1 year after diagnosis.  Antipsychotic, antidepressant and anticonvulsant usage increased in the 3 years following diagnosis, and also with age.  CONCLUSIONS: Prior to PDD diagnosis, more than a third of the patients were on psychotropic medications, a practice that continued and increased after diagnosis.  Psychoactive drug utilization is high and could be of concern if used to compensate for limited access to other treatment modalities such as educational and allied health therapies.