This is a double blind, randomized, mono center, clinical trial with a placebo control group that will be performed in Quads hospital, Sanandaj ,Iran. Inclusion criteria include: major depression based on DSM 4 criteria, physical condition in accordance with ASA Class 1 or 2, and ability and capacity to sign informed consent sheet and exclusion criteria includes: history of major systemic disease, neuromuscular disease, and myalgia. Calculated sample size is 50 patients who will be divide randomly in two groups: Ketamine (study) and normal saline (control). Each patient will be studied at the second and third ECT sessions in a crossover method. Ketamine 30 mg or 2ml 0, 09% saline will be injected in first study ECT session and vice versa in the next ECT session in zero time. Atropine (0.5 mg) will be injected one minute later followed by induction of anesthesia with 1 mg/kg propofol at 30 second later; muscle paralysis will be achieved with 0.5 mg/kg succinylcholine. After reaching paralysis convulsion will be induced by electrical stimulation with first ECT energy doses. Seizure duration, mean arterial pressure and heart rate (at three time: pre-induction, post-induction, and post seizure) myalgia (at 6, 12, 24, and 48 hour after ECT) occurrence of headache and agitation at 24 hour after ECT will be evaluated and be recorded too.