Background: Data are scant on the miss rate of sphincter of Oddi dysfunction if basal pressure in both biliary and pancreatic sphincter segments is not measured during manometry. Methods: Motility tracings with basal pressure measurements of both sphincter segments were retrospectively analyzed. Basal sphincter pressure greater than 40 mm Hg was considered abnormal in either sphincter segment. Results: The study population consisted of 73 subjects (64 women, 9 men; age 45.3 ± 1.6 yr). The basal pressures in the 2 sphincter segments were highly discordant (correlation coefficient = 0.2, p = 0.04). Basal pressures were normal in both segments in 19%, abnormal in both segments in 40%, and abnormal in 1 segment but normal in the other in 41%. The negative predictive value of normal biliary sphincter pressure in excluding sphincter dysfunction was 0.42; when the pancreatic sphincter pressure was normal, the negative predictive value was 0.58. The incidence of pancreatitis with dual duct manometry was comparable to the institutional experience with all sphincter studies. Conclusions: Although the clinical relevance of individually elevated sphincter pressures remains uncertain, there is significant discordance of basal pressures between the biliary and pancreatic sphincter segments. If only the biliary sphincter pressure were to be measured, one fourth of abnormal sphincter pressures would be missed. Therefore, if the first sphincter segment has a normal basal pressure, the other segment should also be evaluated.