Ultrasound remains important in evaluating the gallbladder and biliary tree because of its relative safety, ease of use, availability, and accuracy. Diagnostic considerations associated with gallbladder and biliary sonography are usually straightforward. Pitfalls that can confuse the sonographic interpretation can be divided into three broad groups: technical considerations, anatomic and physiologic variants, and diagnostic mimics. This analysis can be applied to gallbladder ultrasound and sonography of the intra- and extrahepatic biliary tree. It is necessary to appreciate the potential problems, errors, and differential diagnoses to minimize false positive and negative interpretations. Once identified, the pitfalls of gallbladder and biliary sonography usually do not detract significantly from the value of the procedure.