Twelve of 46 female buffaloes with abdominal disorders were diagnosed with omasal impaction. They had been fed finely chopped machine-prepared straw. They were characterised by anorexia, an absence of defecation, abdominal distension, ruminal hypomotility or atony and a suspension of rumination. Omasal impaction was confirmed upon left flank laparorumenotomy on the basis of the size of the omasum and the consistency of its contents. After ruminal evacuation, a long flexible pipe was introduced through the reticulo-omasal orifice and the omasal contents were flushed back into the rumen with water under moderate pressure. Hyponatraemia, hypochloraemia, hypokalaemia and hypophosphataemia were consistent features in most cases. However, two buffaloes that later died had lower levels of plasma chloride, no reticulo-omasal orifice tone and were in an advanced stage of pregnancy. The level of total protein in peritoneal fluid was higher than normal, but the total white cell count was within the normal range. All the animals started passing faeces 36 to 48 hours after surgery. The presence of reticulo-omasal orifice tone and a plasma chloride level above 75 mmol/l were indicators of a good prognosis.