A new adjustable gastric band was developed, consisting of a silicone balloon connected to a subcutaneous port In a closed system. The stoma diameter can be regulated within an extensive range (0-40 mm). The diameter is adjusted individually for each patient and weight loss can therefore be controlled and optimized. We evaluated the application of this new gastric banding procedure in terms of technical feasibility, complication rate and weight loss, and also the relationship between weight loss and pouch volume. Between January 1987 and April 1990 two preliminary studies of 18 and 24 patients respectively were carried out. In the first group there were technical problems resulting in insufficient weight loss. We therefore changed the procedure. In the second group the system thereafter worked as expected. In the second group mean preoperative weight was 132 kg, mean excess weight 60 kg, and mean BMI 45. The mean follow-up was in 21 months. At follow-up mean weight was 91 kg, mean weight loss 41 kg, and mean BMI 31. The mean postoperative stay was 6.0 days. Pouch volume and stoma diameter were followed by regular ondoscopy. There was a distinct relationship between pouch volume and weight loss-the smaller the volume the greater the weight loss.