The dithiasuccinoyl (Dts)-protecting group for amino acids is revoved by thiols (2 equivalents) through the intermediacy of an open-chain carbamoyl disulfide. Starting materials, intermediates, and products can be separated from one another on the standard amino acid analyzer 0.9 × 54-cm column of sulfonated polystyrene resin with 0.2 n sodium citrate buffers. Compounds are detected with the standard ninhydrin-hydrindantin reagent because the hydrindantin acts as a reducing agent and the released amino acid reacts in situ with the ninhydrin to give a purple color. Elution times, integration constants, and the ratios of absorbances at 570 and 440 nm are tabulated. Quantitative conversion of dithiasuccinoyl amino acids to the parent amino acids can be achieved with 0.1 n sodium hydroxide, 0.01 m alcoholic sodium borohydride, 0.1 m triphenylphosphine or 2 mm tri-n-butylphosphine in dioxane-H2O (9:1) or water, and with a variety of thiols under various conditions. The chromatographic methodology is applicable to the determination of rate constants of the pseudo-first-order reductive deprotection of dithiasuccinoyl amino acids.