Conscious sedation, used with or without peripheral or central blocks, is an elective anesthetic technique used for many outpatient procedures. The aim of this study was to evaluate the effects of a single pre-anesthetic dose of betamethasone (4 mg) on intraoperative and postoperative pain in 380 women, 18 to 75 years old, undergoing gynecologic and obstetric surgery (diagnostic curettage, operative and diagnostic hysteroscopy, conization, minilaparoscopy, cone biopsy, endometrial ablation, assisted reproduction techniques, and induced and therapeutic abortion) in a outpatient service. In this randomized, double-blind, placebo-controlled study, the patients were divided into two equal groups according to a computer-generated randomized list. One group received 4 mg of betamethasone i.v. as a premedication (group B), whereas the placebo group (group P) received only saline. All patients underwent the same sedation, associated with a peripheral block. Pain was evaluated using a 5-point verbal rating scale during surgery, after 2 h, and on discharge. In group B, intraoperative and postoperative pain was significantly less frequent than in group P (P < 0.001). Consequently, fewer women belonging to group B requested additional analgesic drugs during and after surgery (P < 0.01). Patients in group B also experienced a greater degree of satisfaction (P < 0.01). Briefly, a single dose of betamethasone seemed to reduce the incidence and severity of perioperative pain after gynecologic outpatient surgery.