Powders of α-lipoic acid (ALA)/cyclodextrin (CD) complexes containing 9-24% (w/w) ALA were prepared to improve the gastrointestinal absorption of ALA. ALA and the ALA/CD complexes, corresponding to 30 mg/kg of body weight of ALA in rats and 600 mg of ALA in humans, were orally administered under fasting conditions. In rats, the area under the ALA plasma concentration/time-course curve from 0 to 3 h (AUC 0-3 h) for the ALA/G2-β-CD^® complex was larger than that for ALA alone. In humans, after administration of 3 ALA/CD complexes with γ-CD, G2-β-CD^® and Isoeleat^®P, the ALA plasma concentration value 0.5 h after administration of the ALA/G2-β-CD^® complex was significantly higher ( p < 0.05) than that for ALA alone, and the AUC 0-3 h value for the ALA/G2-β-CD^® complex was 1.4 times larger than that for ALA alone, although the difference was not significant. We suggest that the water-soluble ALA/G2-β-CD^® complex powder can enhance ALA absorption in rats and humans.