A new spectrophotometric method based on the formation of an ion-pair using bromothymol blue as ion-pair complexing reagent was developed for the determination of mexiletine hydrochloride in capsules. The ion-pair formed was highly coloured and easily extracted with dichloromethane. The calibration curve was linear over the concentration range 1.08-10.8 mug.ml(-1) at lambda(max) = 408 nm (r = 0.9999). The results obtained from the developed method were compared statistically with those obtained by the British Pharmacopeia, method.