A isocratic, selective and accurate LC method of analysis of mexiletine in pharmaceutical preparations has been developed and validated. The method is based on derivatization of mexiletine with 4-chloro-7-nitrobenzofurazan in pH 9.0 borate buffer to yield a yellow product. Chromatography was performed on a C-18 column (150 x 4.6 mm i.d.) with acetonitrile-water 80: 20 (v/v) as mobile phase at a flow rate of 1.0 mL min(-1). UV-visible absorbance detection was performed at 458 nm. The retention time of the mexiletine derivative was 4.10 min, and response was a linear function of concentration in the range 0.5-4.0 mu g mL(-1) (r = 0.9998). The limits of detection and quantification were 0.05 and 0.15 mu g mL(-1), respectively. Method validation revealed precision, sensitivity, and robustness were acceptable. Low RSD values are indicative of high precision, and high recovery values are indicative of the accuracy of the method. Results obtained by use of the proposed method for analysis of the mexiletine content of pharmaceutical a preparation were compared with those obtained by use of the official method. The method has been used for analysis of pharmaceutical preparations.