We studied the academic, cognitive, and behavior profile of 18 patients with Prader-Willi syndrome. All had severe learning disabilities in arithmetic and writing, and the majority were also dyslexic. Their average Full-Scale IQ was 73.7 +/- 8.9, which was 1 SD below normal range, whereas their performance on executive, memory, and visuospatial tasks ranged from 2.1 to 7.0 SD below the expected means. Behavioral problems were measured using the Child Behavior Checklist, on which the majority scored in the pathologic range for social and attention problems, delinquent and aggressive behavior, somatic complaints, and thought problems. Genotypes of the children did not predict cognitive or behavioral profile, nor could behavior be associated with parameters of weight or IQ. In summary, we found that patients with Prader-Willi syndrome have profound learning disabilities and cognitive deficits, greater than expected for their IQ. Behavioral problems, including attention-deficit hyperactivity disorder (ADHD), are also prevalent and impede the overall management of this group of patients. The genotypes were not helpful in predicting cognitive or behavioral patterns.