Patient-controlled analgesia (PCA) is a concept that permits patients to administer a prescribed dose of narcotic to themselves when they experience pain. Six patients developed colonic pseudoobstruction after the use of morphine sulfate administered via a PCA infuser. Early recognition and prompt treatment make this a transient, reversible illness. Treatment includes discontinuing the use of the PCA morphine, eliminating oral intake, ensuring adequate hydration and electrolyte balance, placing a nasogastric tube, rolling the patient, and closely observing for signs and symptoms of worsening colonic distention and possible rupture.