We assessed whether adding promethazine to the syringe containing morphine for patient-controlled analgesia (PCA) decreases nausea after gynecologic surgery. Patients were assigned randomly to receive PCA (morphine 1.5 mg, 6-min lockout interval) with or without promethazine (0.625 mg/PCA dose, providing an average of 17.6 mg/24 h). Assessments included a visual analogue scale (VAS) for nausea (0 = none, 10 = worst possible) at scheduled times, rescue therapy requirements, and a maximum symptom-therapy score that provided an aggregate assessment of nausea intensity, duration, and response to rescue therapy (0 = no nausea; 1 = mild; 2 = moderate, requiring droperidol; 3 = severe or persistent, requiring droperidol; 4 = requiring droperidol + transdermal scopolamine; 5 = unrelieved). Nausea scores on the visual analogue scale at 2, 6, 8, and 24 h and use of rescue droperidol identified no significant differences between the groups. However, symptom-therapy scores differed significantly, with median values of 0 and 2, respectively, for the promethazine-treated and control groups. We conclude that simultaneous titration of morphine and promethazine decreases nausea associated with PCA therapy; the difference may best be appreciated with use of the combined symptom-therapy score.