The morphine-Prostigmin test (MPT) has been advocated as a diagnostic test for identifying patients with papillary stenosis. We studied 14 patients referred for possible papillary stenosis with the MPT and ERCP sphincter of Oddi manometry. The response to the MPT (symptoms, serum amylase/lipase values) was evaluated by multiple criteria. The MPT was also done on 6 volunteer control subjects. Operative evaluation of the sphincter of Oddi was obtained in 8 of the 14 patients. There was no correlation between the results of the MPT and ERCP manometry or operative findings. There was good correlation, however, between ERCP manometric findings and operative assessment of the sphincter of Oddi. Fifty percent of the volunteer subjects had a significantly positive enzyme response to the MPT. In our experience the MPT does not reliably detect patients with papillary stenosis.