The physiological condition of the adult learner as related to his learning capability is discussed. The design of the instructional process, the selection of learning tasks, the rate at which instruction occurs, and the nature of the instructional setting may all be modified by the instructor to accomodate the variable physiological conditions of the adult learner. Every adult learner will experience some deficiency in auditory or visual perception. The physiological changes that occur in the eye are discussed in relation to visual acuity, variability to illumination, color perception, and visual perception. Hearing is discussed as to auditory discrimination and emotion and hearing. The changes in sensory acuity that result in reduced perception cannot be altered, but the instructor can take some action as compensation. Since adequate perception of the learning stimulus is a pre-requisite of learning and, consequently, of memory, an instructor can enhance the retention of learned material by insuring the accurate and complete perception of the stimulus. Psychomotor skills and verbal communication are directly affected by physiological factors. An adult educator can help the adult learner to understand his physical difficulties and ways of overcoming their interference with learning. Eleven references for additional study are provided. (For related documents, see AC 014 525-526, 528-534.) (DB)