Studied the relationship between degree of mental retardation, associated psychiatric disorders and sociodemographic characteristics in a retrospective review of the case records of all 12-18 yr old patients attending a psychiatric clinic in Saudi ArabiResults show that the most reported psychiatric diagnosis in those with borderline mental retardation was attention deficit hyperactivity disorder (ADHD, 16.8%), dual diagnosis of ADHD and expressive language disorder disorder (11.7%), and non-specific behavioral disturbance (10.9%). The most reported psychiatric diagnosis in those with moderate-severe mental retardation were autistic disorder (15.8%), ADHD (10.5%) and non-specific behavioral disturbance (10.5%). It is concluded that children and adolescents with mental retardation have a high rate of psychiatric disorders, and the degree of mental retardation correlates with the behavioral disturbance and the severity of psychiatric disorders.