Background: The identification and treatment of psychiatric disorders in individuals with autism spectrum disorders (ASD) and ID presents many challenges. We describe the development of a professional network, together with a standardized protocol for clinical assessment, designed to promote clinical competence and professional development in eight clinical centers responsible for providing mental health services to autistic individuals with ID across all four health regions of Norway. Specific aims to describe: (1) patterns of psychiatric and behavior problems in patients treated by the network, (2) patterns of change over time, and (3) the relationship between psychiatric disorders and behavior problems. Method: A standardized protocol was used to assess individual progress in 132 patients (inpatients and outpatients) with autism and ID over 2 years (at referral (T1), after 1 year (T2), and after 2 years (T3)). Changes in psychiatric symptoms and behavior problems were assessed with the Psychopathology in Autism Checklist (PAC) and Aberrant Behavior Checklist (ABC). Results: Patients showed significant (p < .001) improvements from T1 to T2 on the psychosis, depression and anxiety subscales of the PAC, but no significant improvement on the obsessive compulsive disorder (OCD) subscale. Improvements were maintained from T2 to T3. Patients showed significant (p < .01) improvements on the ABC total score and on all ABC subscales except inappropriate speech from T1 to T2; these improvements were maintained from T2 to T3. Discussion: The combination of a professional network and a standardized protocol for clinical assessment has promise as a strategy for improving professional competence and facilitating specialized mental health services for autistic individuals with ID and psychiatric disorders across an extensive geographical area.