In order to study the stability of allicin. an active constituent of garlic extract, the rate of formation of allicin from allicin and that of decomposition of allicin to volatile oil/sulphides has been determined by chloramine-T method. The effect of acetic acid (5-30%), ethanol (5-30%), buffers (pH 4.0-6.0) and temperature (30-50 degreesC) on the rate of formation of allicin and on the rate of its further decomposition to volatile oil has been studied. It has been observed that the decomposition of allicin decreases with an increase in the strength of acetic acid and increases with an increase in the pH of macerating medium. The increasing strength of ethanol in macerating medium had a little effect of the rate of decomposition, which was found to be maximum at an incubation temperature of 35 degreesC.