Solvent-free &agr;-lipoic acid is produced by dissolving a) the &agr;-lipoic acid to be purified in aqueous alkaline solution, or dissolving the salt thereof in water and adjusting an alkaline pH, b) removing solid impurities present where appropriate from the aqueous solution from stage a), c) adjusting the aqueous solution from stage a) or b) to a pH of from 1.0 to 5.0 with the aid of an acid and d) isolating the precipitated &agr;-lipoic acid by known methods. This results in a solvent-free &agr;-lipoic acid with improved chemical purity.