To evaluate the diagnostic accuracy of gallbladder ultrasound performed by emergency physicians (EPUS) in patients with right upper quadrant (RUQ) and epigastric (EPI) pain, adults>18 years of age with RUQ or EPI pain were prospectively evaluated by physical examination, laboratory data, and EPUS followed by a blinded radiology department ultrasound (RADUS). Diagnostic categories included: "normal gallbladder"; "uncomplicated symptomatic cholelithiasis" (uncomplicated SCL; stones present but symptoms and signs relieved and no abnormal blood-work); or "complicated symptomatic cholelithiasis" (CSCL; stones and positive symptoms and signs including abnormal blood-work). Final Emergency Department patient assessments based on the RADUS were compared to the EPUS. Over 2-years, 127 patients were enrolled. The sensitivity of the EPUS for detecting stones was 94% (positive predictive value 99%; specificity 96%; negative predictive value 73%). In conclusion, the EPUS is a highly sensitive and reliable indicator of the presence of gallstones.