Examined the nature and development of adaptive behavior (AB) deficits in 200 moderately to severely retarded children, adolescents, and adults (the majority aged 6-20 yrs) in the West Bank. A case worker acquainted with this population rated the ABs of the Ss. While Ss' AB levels were generally depressed, their greatest deficits were in the areas of basic knowledge, general knowledge, and social adjustment. Significant differences between the 3 age-groups suggest that Ss' AB did not conform to expected developmental trends. Implications are offered for special educator awareness of the potentially negative influence of culture on AB.