It remains controversial whether manometric parameters recorded from the pancreatic and biliary segment of the sphincter of Oddi (SO) differ. We therefore studied 48 consecutive patients (40 women, 43 +/- 11 years) with suspected SO dysfunction, in 33 of whom successful dual-duct SO manometry was obtained. Measures of concordance between the two duct segments were moderate for basal sphincter pressure (K = 0.31) and for contractile frequency (0.35), and were low for peak pressure (0.15) and for proportion of retrograde propagation (-0.19). There was also low concordance (-0.13) for the overall manometric diagnosis, and in 48% (CI 31-66%) of patients a conflicting diagnosis (normal/abnormal) was obtained from the two ducts. There was no evidence of a differential motor effect of CCK on either duct, nor were there significant differences in the rate of manometric abnormality according to the order of initial duct cannulation. These results indicate that, if technically feasible, dual-duct manometry of the sphincter of Oddi is required for diagnostic precision.