Cognitive profiles of performance were obtained from a selected group of adolescent subjects with mental retardation (MR) (n = 32; mean age: 15.4 years, S.D. = 3.7) by means of an ad hoc neuropsychological battery. On the basis of each subject's IQ, the experimental sample was divided into three homogeneous subgroups (severely, moderately and mildly retarded) and cognitive performances obtained in the battery tests were compared. Subsequently, in order to clarify the qualitative aspects of MR, the cognitive patterns of subjects with the same IQ and chronological age were examined. Altogether, from a neuropsychological point of view, the results of this study seem to support the hypothesis that MR is a heterogeneous condition of cognitive deficits (some abilities are better preserved than others) and indicate that a set of multiple tests exploring single cognitive functions is needed in order to describe cognitive profiles in MR.