A case involving a fatal overdose of mexiletine is presented. Quantitation of the drug was accomplished by gas chromatography with a flame-ionization detector. The presence of mexiletine was confirmed by gas chromatography-mass spectrometry. Toxicological analysis revealed the following tissue distribution of mexiletine: heart blood, 44.8 micrograms/mL; femoral blood, 10.0 micrograms/mL; vitreous, 8.6 micrograms/mL; liver, 171.6 micrograms/g; brain, 84.0 micrograms/g; and gastric contents, 1464 mg.