The reaction of half esters derived from polyhydric alcohols including ethylene glycol or glycerol has been investigated. The reactivity of half esters toward the reaction with primary amine has been compared with the reactivity of ordinary esters. The reaction was enhanced by introducing hydroxyl groups into the alcohol moiety of esters, and it took place in solutions under mild conditions. The reactivity enhancement was related with the number of hydroxyl groups in the half esters; the half ester derived from glycerol reacted easily with amine with a much faster rate than ordinary esters. The reactivity enhancement owing to the hydroxyl group is explained by an interaction of the hydroxyl group with amine in solutions. A tentative experiment was carried out to prepare polyamide under mild conditions by using bis(2-hydroxyethyl) terephthalate.