We studied the time of onset and other clinical features of biliary pain in 54 patients living in Northern Italy. All patients had cholelithiasis documented by ultrasonography. The time of onset of pain followed a circadian periodicity with its peak occurring at 9:30 p.m. The typical biliary pain was steady, mostly localized in the right upper quadrant of the abdomen or the epigastrium, lasted over 1 h, and required analgesics for relief. The pain was not related to meals or body position. What precipitates biliary pain is still an enigma.