A wide range of secretory (salivation, gastric acid and bile secretion) and motor functions (rumination, esophageal and anal sphincter contraction, gastric and colonic motility) have been successfully modified using operant conditioning procedures or biofeedback training. The clinical syndromes to which these studies have been addressed include rumination, reflux esophagitis, hypersecretion of acid associated with peptic ulcer, irritable bowel syndrome, and fecal incontinence. The available evidence strongly suggests that biofeedback is effective and is the treatment of choice for some types of fecal incontinence, and the evidence supports the effectiveness of operant conditioning for the treatment of intractable rumination in infants or retarded individuals. There is suggestive evidence that a nonspecific biofeedback technique, EMG biofeedback for skeletal muscle relaxation, may contribute to the healing of peptic ulcers, but the data are so far inconclusive. Biofeedback approaches to the treatment of other clinical syndromes are at the investigational stage only, and no predictions can be made regarding their efficacy.