A simple, sensitive, accurate and rapid spectrophotometric method for the determination of some anthelmintics that are used in veterinary medication is described, based on the formation of an ion pair complex with bromocresol purple (BCP) and bromocresol green (BCG). Drugs analyzed are piperazine hexahydrate, tetramisole hydrochloride and metronidazole. The drugs were determined either in pure powdered forms or in pharmaceutical formulations using the standard addition technique. The sensitivity, precision and accuracy of the method was discussed and the results compared with the official method of British Pharmacopoeia (B.P. 1993).