A simple accurate and precise spectrophotometric method was proposed for determining mefenamic acid in pure form as well as dosage forms. The procedure is based on the oxidative coupling reaction of mefenamic acid with 4-aminoantipyrine reagent in an acidic medium (pH 3.6) in the presence of N-chlorosuccinimide as oxidizing agent to produce an intense colored and water-soluble product which exhibits maximum absorption at 588 nm. Beer’s law is obeyed in the concentration range of 10- 250 g mefenamic acid in a final volume of 25 ml (0.4 -10 ppm). The proposed method was applied to determine mefenamic acid in pharmaceutical preparations. The amount of mefenamic acid found are very similar to those obtained by a standard method.