A randomized controlled trial was carried out with the purpose to determine the effectiveness of EMG-biofeedback in the treatment of chronically constipated elderly patients with dyssynergic defecation as compared to a control condition characterized by information about the bowel functioning and counseling focused on the behavioural mechanisms involved in the defecation. With this purpose, after an initial assessment period (4 weeks), 30 chronically constipated elderly patients with dyssynergic defecation (11 males, 19 females) were randomly assigned to either EMG-biofeedback group (n = 15) or control group (n = 15). The results shown significant improvements in psychophysiological measures (EMG-activity during straining to defecate and anismus index), as well as in clinical variables (frequency of defecations per week, sensation of incomplete evacuation, difficulty evacuation level and perianal pain at defecation) only in the EMG-biofeedback group. The clinical benefits of this behavioural treatment were maintained at the follow-up period 2 months later.