The capacity for absorption after a small bowel resection depends upon the remaining length of intestine. This is important in planning nutritional therapy and affects surgical policy should further resection appear necessary. In 18 patients, the remaining small bowel length from the duodenojejunal flexure had been measured at operation and found to be less than 200 cm; this was compared with a measurement obtained by one observer using an opisometer on a subsequent barium follow-through (BaFT) examination. A significant correlation (p less than 0.001) of 0.72 was found. Radiographic measurement was easiest when the bowel was short (less than 150 cm) and all seen on one film with no overlapping loops. A residual small intestinal length of less than 200 cm measured from a BaFT radiograph is sufficiently accurate to formulate management decisions.