Costs were not discounted and prices and quantities were not analysed separately. Costs were based on average charges at Stanford University Hospital and clinics. The costs included charges for presurgical visits and counselling, preoperative examination and anaesthesia, charge for the operative suite, fees for anaesthesia and surgery, charges for a postoperative visit and charges for visits in connection with GnRH-a therapy and costs of the drug. From these a charge for initial treatment per patient was calculated under each strategy. The total costs were modelled on 100 hypothetical patients of whom 35 would need repeat surgery, which was included in the total cost estimate. Costs for other pathology in which endometriosis was not the cause of symptoms were not estimated. No date was given for prices.