Upright walking posture was successfully trained, maintained, and transferred to a new setting in a 28-year-old profoundly retarded adult. An apparatus in the S's cap and vest provided reinforcement (radio) when the S's head was up. The first four phases of the study demonstrated stimulus control in the training setting, while the next nine phases evaluated the degree to which erect posture in the transfer setting could be controlled by manipulating variables (such as frequency of walks and experimenter control of the reinforcement) in the training setting. Results indicated that maintenance of posture gains in the transfer setting was excellent across a 6-month follow-up phase. (DB)