Abstract: A no-base type, aqueous alkali-based hair-straightening composition having a pH between 12 and about 14 initiates and enhances the permanent hair-straightening effect. The hair-straightening composition comprises, as an active hair-straightening agent, a strong alkali, and a water-soluble hair-straightening initiating agent. The initiating agent is a mercapto (C.sub.4 -C.sub.6) dicarboxylic acid having a sulfhydryl functional group on a carbon atom alpha to one or both of the carboxy acid groups, salt thereof or derivative thereof, and is a hair keratin-disulfide reducing agent. The initiated composition particularly augments and enhances the permanent hair-straightening benefits of sodium hydroxide, yet substantially overcomes negative hair conditioning problems normally associated therewith. Thiomalic acid and 2,5-dimercaptoadipic acid are preferred initiating agents. Also disclosed is a hair-straightening system and method for straightening hair with the foregoing compositions.