PROPOsE: To compare the postoperative analgesic effects of electroacupuncture, morphine or sham acupuncture in dogs undergoing mastectomy.METHOds: Thirty client-owed dogs undergoing to mastectomy were randomly assigned to three groups of 10 animals each and received either morphine (T-M), the electroacupuncture (T-EA) or sham procedure (T-Sham). Pre-anesthetic medication was acepromazine (0.05 mg kg -1 , IM). Anesthesia was induced with propofol (4 to 5 mg kg -1 , IV) and maintained with isoflurane. Postoperatively pain degree was assessed using a numerical rating scale. Dogs were scored at 1, 3, 6 and 12 hours post-extubation. If the pain score was ≥6, supplemental morphine was administered. Serum cortisol concentration was measured before pre-anesthetic medication, at 45 minutes after the anesthetic induction, and at 1, 3 and 6 hours post-extubation. REsuLTs:The pain score did not differ among the treatments, but rescue analgesia was lower in the T-EA group (2 of 10 dogs), when compared with T-Sham (6 of 10 dogs) and T-M (6 of 10 dogs) groups. Serum cortisol concentration did not differ among the treatments.CONCLusION: Electroacupuncture reduces the postoperative analgesic requirement and promotes satisfactory analgesia in dogs undergoing mastectomy.