To determine the frequency and magnitude of interobserver variability, 50 sphincter of Oddi manometry tracings were read by three separate physicians experienced in reading such manometry. Ninety station pull-throughs were read, and attention was focused on the reference duodenal baseline pressure and two methods of reading the basal sphincter pressure. A high degree of correlation was found among the three observers with correlation coefficients of > 0.9 for reading baseline duodenal and basal sphincter pressures. Differences in basal sphincter pressure readings were greatest in patients with very high basal sphincter pressure. The most clinically relevant parameter was thought to be the mean basal sphincter pressure. All three observers agreed on normal (mean basal pressure < or = 40 mm Hg) versus abnormal (mean basal pressure > 40 mm Hg) in 82% to 90% of tracings. When the definition of agreement was broadened to include patients with pressures of 40 +/- 3 mm Hg (37 to 43 mm Hg), the observers agreed 87% to 94% of the time. Overall, these findings are thought to indicate that interobserver variability for reading sphincter of Oddi manometry is minimal when the observers are experienced in reading these tracings.