The aim of this study was to examine whether mentally retarded individuals show a specific motor performance deficit on measures of reaction time, aiming, and dexterity. 23 mentally retarded adolescents and two control groups of 22 nonretarded persons of the same mental age and 20 nonretarded persons of the same chronological age were tested. Motor performance measures for retarded persons were considerably longer than those of nonretarded persons of the same chronological age and the retarded than for the nonretarded adolescents of the same mental age. Reaction times across groups were faster for the sound than for the light signal. No difference in RT for fine movement was observed. Differences among the various motor performance measures for retarded and nonretarded subjects are confirmed. The aim of this study was to examine whether mentally retarded individuals show a specific motor performance deficit on measures of reaction time, aiming, and dexterity. 23 mentally retarded adolescents and two control groups of 22 nonretarded persons of the same mental age and 20 nonretarded persons of the same chronological age were tested. Motor performance measures for retarded persons were considerably longer than those of nonretarded persons of the same chronological age and the retarded than for the nonretarded adolescents of the same mental age. Reaction times across groups were faster for the sound than for the light signal. No difference in RT for fine movement was observed. Differences among the various motor performance measures for retarded and nonretarded subjects are confirmed