In order to specify the role of peripheral muscular tissue in ammonia metabolism, we studied, in rats, the variations of ammonia and glutamine levels in arterial and femoral venous blood after hepatectomy and abdominal evisceration with nephrectomy. In non-fasting rats this operation was immediately followed by an important hyperammonemia which was due to ammonia muscular release; glutamine blood levels increased only slightly without any modification in their arterio-femoral venous differences. The hyperammonemia induced by hepatectomy-evisceration was greatly reduced in animals which had been fasting for 48 hours but was not modified by a 72hrs preoperative sucrose feeding. These nutritional conditions did not change the blood glutamine variations which were first related to the abdominal evisceration. Indeed, in abdominal eviscerated rats without hepatectomy there was an important hyperglutaminemia with only a slight increase in blood ammonia. These results indicate that in rat 1) the liver plays an important part in skeletal muscle ammonia metabolism, 2) this metabolism is related to food ingestion, 3) the gastrointestinal tissue intervenes in glutamine metabolism.