Postoperative use of as-needed intramuscular narcotics is potentially hazardous in frail elderly patients. Patient-controlled analgesia (PCA) allows patients to self-administer small boluses of narcotic, allowing better dose titration, enhanced responsiveness to variability in narcotic requirements, and reduction in serum narcotic level fluctuation. Although theoretically useful, this method has not bee well studied in the elderly or medically ill. A prospective controlled trial among 83 higher-risk elderly men after major elective surgery compared PCA containing morphine sulfate with intramuscular morphine injections as needed (mean [+/- SD] age, 67.4 +/- 5.6 vs 67.0 +/- 6.3 years). Subjects had a variety of medical illnesses, including chronic lung disease (57%), coronary artery disease (43%), heart failure (13%), and liver disease (12%). Preoperative and postoperative assessments included chest roentgenograms; daily mental status and pulmonary function testing; twice-daily serum morphine levels; and oxygen saturation values, linear analogue pain and sedation scores, and vital signs every 2 hours. Care was taken to optimize narcotic administration in control subjects as well as PCA subjects. Analgesia was significantly improved by PCA (3-day mean pain score, 40.5 +/- 18.0 vs 32.5 +/- 15.0), without an increase in sedation. Significant postoperative confusion (18% vs 2.3%) and severe pulmonary complications (10% vs 0%) occurred significantly more frequently in intramuscular-treated controls. Patient-controlled analgesia was quickly mastered by most patients; no major problems referable to its use occurred. Patients who had previously received intramuscular injections reported that PCA was easier to use and provided better analgesia. Serum morphine levels showed significantly less variability on postoperative day 1 with PCA, compared with intramuscular injections. We conclude that PCA is an improved method of postoperative analgesia in high-risk elderly men with normal mental status, compared with as-needed intramuscular injections.