Aim: Individuals with congenital insensitivity to pain with anhidrosis (CIPA) are reported to have mental retardation* but to our knowledge no detailed study on the subject has ever been published. The present study assessed and documented cognitive and adaptive behaviour among Arab Bedouin children with CIPA. Methods: Twenty-three Arab Bedouin children (12 females, 11 males) with CIPA aged between 3 and 17 years (mean 9y 7mo, SD 4y 2mo) were assessed. They were compared with 19 healthy siblings of the affected children aged between 5 and 13 years (mean 8y 11mo, SD 2y 10m). All of the children in the comparison group, but only half of the CIPA group, were attending school. The children were evaluated using a standardized, non-verbal intelligence test, the Leiter International Performance Scale - Revised, and an adaptive behaviour questionnaire, the Vineland Adaptive Behaviour Scales, 2nd edition. Results: Based on scores on the intelligence test and the adaptive behaviour scale, children with CIPA functioned in the mental retardation range (mean IQ scores: CIPA group 53.8, comparison group 83.32 [. p<0.001]; adaptive behaviour: CIPA group 68.1, comparison group 104.88 [. p<0.001]). IQ was significantly higher among the children with CIPA aged up to 7 years 11 months than among the older children 73.83 vs 45.21 (p<0.001). Interpretation: As a group, the younger children with CIPA may be functioning above the mental retardation range. We propose that early intervention addressing these children's needs and developing an appropriate educational system, might improve their outcome.