A rapid method for the analysis of dansylated essential and branched-chain amino acids (BCAAs) by micellar electrokinetic capillary chromatography (MECC) is reported. Optimization of analytical conditions has been carried out, evaluating the influence on the performance of several parameters such as sodium dodecyl sulfate (SDS) concentration in the running electrolyte, temperature, and voltage. The effect of the addition of small amounts of isobutanol to the electrolyte has also been investigated. The best separation in the shortest time with a 37 cm capillary was obtained employing a 20 mM Borax buffer (pH 9.1) + 70 mM SDS at 25 degrees C and 20 kV. Under these conditions a mixture of nine essential amino acids was analyzed in 7 min, while separation of BCAAs occurred in less than 4 min. Using a shorter capillary (20 cm to the detector), the BCAA separation was performed in only 2.5 min. The method was applied to the quantitative analysis of amino acids in three commercial nutraceutical preparations. Assessment of analytical performance in terms of precision, linearity, and limit of detection has also been reported.