Separation of Li-6 and Li-7 isotopes by CZE was demonstrated. The BGE contained 5 mM 4-aminopyridine, 0.9 mM oxalic acid, 0.25 mM CTAB, and 0.25% w/v Tween 20 (pM = 9.2). The running conditions were +25 kV at 30 degrees C with indirect photometric detection at 261 nm. Under optimal experimental conditions, the analysis time was less than 21 min. Separation of Li preparations with mole fraction of Li-6 ranging from 3.44 up to 90.38% was demonstrated.