A tube system for the collection of uncontaminated small-bowel juice is described. It consists of an outer guide tube, its distal end being closed by a membrane, and an inner aspiration tube. When the outer tube is placed at the desired site of aspiration, the membrane is perforated by advancing the sterile inner tube. The device was tested in 90 healthy human volunteers. The procedure was completely or partly unsuccessful in 9 cases (95% confidence limits, 4.7-18.0). Median intubation time was 12 min; range, 5-14 min. The time used for aspiration of 5 ml of intestinal juice varied from 1 to 30 min; median, 10 min. The site of aspiration in jejunum distal to the ligament of Treitz varied from 0 to 14 cm; median, 3 cm. No complications of the procedure were registered.