Sixty unpremedicated outpatients undergoing elective extracorporeal shockwave lithotripsy (SWL) using a Dornier MPL 9000 lithotripter were randomly assigned to receive either propofol-alfentanil (PA group; N = 30) or midazolam-alfentanil (MA group; N = 30) by a patient-controlled analgesia (PCA) device for sedation and analgesia. Although pain intensity scores were lower after 20 minutes and sedation was more pronounced in the MA group, both drug regimens produced satisfactory sedation and analgesia and allowed the maximum number of shockwaves to be given. Alfentanil consumption was less in the MA group (P < 0.05). Both groups were hemodynamically stable. The patients in the MA group had slower ventilation rates, lower oxygen saturation, and higher end-tidal carbon dioxide levels. Use of MA was associated with more episodes of oxygen desaturation to < 90% (30% vs. 11%; P < 0.05). One patient in the PA group and three patients in the MA group developed bradypnea (< 10 breaths/min). Patient satisfaction was very high with the two sedative-analgesic techniques. Propofol and midazolam, when given in combination with alfentanil using a PCA pump, may provide safe, effective analgesia and sedation during lithotripsy. Patient-controlled sedation and analgesia may provide optimal conditions for SWL of urinary tract stones and is a useful alternative to other forms of anesthesia and analgesia.