Patient controlled analgesia improves titration of analgesic drugs, minimizing individual pharmacodynamic differences between patients, during the postoperative period. We describe the efficacy and the safety of intravenous PCA, based on the follow-up of 300 patients, recovering from upper and lower abdominal surgery. Successful use of PCA requires the choice of two important parameters: the PCA bolus and the lock-out period. In our experience, we only prescribed morphine, with a PCA bolus of 0.5 or 1 mg and a lock-out period of 5 or 10 minutes. Nurses were educated to change the syringes and to assess analgesia and the respiratory function. Patients were mostly hospitalized in surgical wards and only 16% of patients were treated in an intensive care unit. Patient's acceptance proved to be excellent and only 4 patients were not satisfied with PCA therapy. The incidence of respiratory depression was low (0.02%) and only one patient required naloxone. The side effects were dysphoria, nausea, pruritus and urinary retention; their incidence was low.