Procedures are described that facilitate the immunoelectrophoretic analysis of the carcinogen-binding protein ligandin. Rocket immunoelectrophoresis is performed at pH 4.9 in agarose gel containing carbamylated antiserum thereby promoting more rapid migration of ligandin, pI 9.0, into the gel. This method is used as a basis for quantitative crossed immunoelectrophoresis using either electrophoresis or isoelectrofocusing of ligandin in the first dimension.