Cholestasis is not a disease but rather a symptom of many diseases. It is defined as a pathologic state of reduced bile formation or flow. More specifically, cholestasis is any condition in which substances normally excreted into bile are retained. The serum concentrations of conjugated bilirubin and bile salts are the most commonly measured. In this issue, an international list of expert authors address topics such as the mechanisms of cholestasis and the insights gained from several new studies, the role of mitochondria have in cholestatic reactions to toxic drug effects, the medical treatment of cholestasis, and cholangiocarcinoma.