Thirty-four mentally retarded, institutionalized adults were subjects in a study of the effects of sensorimotor integrative treatment procedures on sensorimotor development. The 25 subjects in the experimental group received group sensorimotor integrative treatment in addition to regular institutional programming; the 9 subjects in the control group received only the regular institutional programming. The Sensorimotor Performance Analysis was used to test sensorimotor performance of all subjects four times during the 12-month study. Results showed that both the experimental group and the control group made gains in sensorimotor development, with no significant differences between groups. The findings indicate that treatment procedures for improving sensorimotor development of the mentally retarded adult need further examination so that appropriate modalities can be developed. Periodic reassessment of the client following completion of treatment is suggested because of possible delays in improvement of sensorimotor development.