This study was designed to determine whether a pregnant sow could be maintained under conditions of prolonged general anesthesia in order to provide access to prematurely delivered piglets for purposes of acute experimentation. Fifteen time-dated pregnant (90% of gestation) sows were preanesthetized with intramuscular xylazine (Rompun Mobay Pharmaceutical, Shawnee, KS)/ketamine (Aveco Pharmaceutical, Fort Dodge, IA). After anesthesia was induced with intravenous sodium thiopental, the animals underwent tracheotomy and mechanical ventilation. The electrocardiogram was monitored externally; systemic arterial pressure was supervised by the insertion of a brachial artery cannula; and urine output was determined by inserting a cystostomy tube. A surgical plane of anesthesia was achieved by the "balanced" technique: an inhalant, isoflurane, supplemented by intravenous doses of sufentanil citrate, propofol (Stuart Pharmaceuticals, Wilmington, DE), and vecuronium. Sows were maintained under general anesthesia for an average of 12 h; piglets were delivered, one or two at a time, by a modified cesarean section technique. No sows or piglets were lost to anesthetic complications. It is concluded that, with appropriate precautions, pregnant sows can be anesthetized for a prolonged period of time, and provide viable premature neonates for acute experimentation.