Abstract: A method for purity control of tetracycline with capillary electrophoresis is described.It allows the complete separation of tetracycline and its main impurities 4-epitetracycline,anhydrotetracycline,4-epianhydrotetracycline and 2-acety-2-decarboxamidotetracycline.Less important chlortetracycline and demethyltetracycline can also be resolved.Method development was undertaken with a mixture consisting of tetracycline and its main impurities mentioned.Using an uncoated fused silica capillary,the infiuences of buffer pH,buffer concentration,temperature and applied voltage were systematically investigated.UV-detection was performed at 270 nm.A relative standard deviation of 1.9% was obtained for tetracycline.The results are compared with those of liquid chromatography and existing capillary electrophoresis.