Ketamine (CI-581, Ketalar, Ketaject, or Ketavet), a cyclohexylamine, has been in use for over 20 years (clinically avaiable since 1970) and has been established as a safe and efficacious agent. It has been used as an analgesic demonstrating an exceptional margin of safety in ninety-seven series involving 17,550 administrations (1). It has been administered in parturients for vaginal delivery as well as for Caesarian section without adverse effects to either the patient or the neonate (2). It can be administered i.v., i.m., p.o., p.r., epidurally and intrathecally and it has even been given on an outpatient basis. This study will test the hypothesis that ketamine is an effective treatment for obstructive sleep apnea. This hypothesis is based on evidence that suggests that ketamine maintains upper airway muscular tone (1,2) and that tone may even be augmented leading to an unobstructed airway during anesthesia.(3-7). The study will involve twelve patients with documented obstructive sleep apnea, previously diagnosed via polysomnography, that have not had any prior therapeutic intervention. It will be a double-blind, placebo-controlled study. The patients will be in the age range of 21-65 years. The study will involve two nights of repeat polysomnography during which the patients will receive either placebo (normal saline) of ketamine intravenously. Ketamine will be administered in subanesthetic doses. Plasma levels of ketamine and its major metabolite, norketamine will be assayed via blood sampling every two hours. If ketamine can be proven to be an effective pharmacological agent against obstructive sleep apnea, then further studies can be undertaken to evaluate the specific oral doses needed to treat this condition.