The kinetics and mechanism of hydrolysis of a series of substituted benzylidene benzoylhydrazones (X - BBH) have been studied at five different temperatures in the range 25 - 45"c by U.V. -visible spectrophotometry . The hydrolysis reactions were found to follow first - order kinetics . A mechanism has been postulated in which the attack of water on the protonated substrate is subject to general base catalysis . This mechanism has been supported by the effect of anion concentration of buffer , at constant pH , on the observed rate constant . The Bronsted &value for the hydrolysis reaction is 0.73. Hammett correlations, Arrhenius and thermodynamic parametres have been evaluated and discussed . The pKa values for the conjugate acids for benzylidene benzoylhydrazones derivatives ( X - BBH )have been determined.