Prevalence of adolescents with conduct disorder (CD) has been calculated between 4 y 10%.To estimate the prevalence of mental retardation in Colombian adolescent offenders, using the Wechsler Intelligence Scales for Children Revised (WISC R).106 male adolescent offenders with CD, aged 12 to 16 years, and attending to institutions of re education in Medell n Colombia were selected in a randomized approach. WISC R Hispanic version was administered to the sample, using 4 verbal (information, vocabulary, similarities and arithmetic) and 4 performance (Picture completion, block design, picture arrangement, and digit symbol) subtests for calculating verbal, performance and full scale IQs (VIQ, PIQ, and FSIQ), according to the manual instructions.43 participants (40.6%) obtained a FSIQ < 70, then they were categorized as mild mental retardation. 34 offenders (32.1%) had a FSIQ between 70 and 84, then they were classified as people with borderline intellectual functioning, only 29 participants (27.4%) obtained a FSIQ over 85.72.7% of the institutionalized adolescents offenders had low intellectual functioning, which may be interfere with the re education programs.