Serum protein electrophoresis is of certain diagnostic interest. We report a case of unusual electrophoresis associated with cholestatic jaundice complicating a cholangiocarcinoma. The study involved a 55-year old patient hospitalized for the exploration of cholestatic jaundice. Capillary electrophoresis showed bisalbuminemia diagnosed based on the thickening of the bottom of the albumin peak and a supernumerary peak X. Second electrophoresis with Hydragel showed the disappearance of the two above abnormalities which was the proof that bisalbuminemia was acquired and of the lipidic nature of the Pic X. In our case, the most likely cause was the presence of interfering substances such as free bilirubin (hyperbilirubinemia), lipids (hyperlipidaemia) and bile acids. Bisalbuminemia in a patient with similar electrophoretic picture should suggest the search for underlying diseases.