In the present article we consider general anesthesia as a means of exploring questions regarding unconscious influence. The primary questions addressed in the research are whether surgical patients who are under adequate general anesthesia unconsciously perceive auditory information and whether they can benefit from such information. In addition, we consider the relevance of individual hypnotic ability for perceptual processing in this context. Ninety-six adult patients, undergoing elective abdominal hysterectomy, were randomly allocated to one of four tape-recorded conditions: therapeutic suggestions, melodies, (...) suggestions-plus-melodies, or silence. Double-blind conditions were satisfied in every respect. Patients received a standardized, but typical, "balanced" anesthetic, and level of anesthesia was adequately monitored. Following surgery, all patients received their analgesic medication from a patient-controlled device. Patients who were played therapeutic suggestions used a significantly smaller dose of morphine than patients who were not played suggestions. Although hypnotic ability was not significantly associated with therapeutic outcome, high but not low hypnotizable patients accurately guessed whether they were played suggestions. No compelling evidence for memory of melodies was obtained. (shrink)