Abstract: Due to key role of ABA in drought tolerance, it was envisaged to develop a method for extraction and quantification of Abscisic Acid (ABA) and to isolate a ABA responsive and water deficit stress inducible gene from rice. A new analytical method which ensures the integrity of ABA during extraction, clean-up and estimation, was developed. ABA was quantified at different developmental stages of immature seeds and leaves. ABA content in leaves increases when a plant is exposed to water deficit stress but it decreases as the leaves approach maturity. ABA concentration also increases as developing seeds attain maturity. An ABA responsive gene of 264 bp was isolated which shows induced expression under water deficit stress. The gene has two domains, one belonging to aspartate aminotransferase super family of pyridoxal phosphate dependent enzymes and the other showing similarity with Major Facilitator Super family (MFS) of secondary transporters that include uniporters, symporters and antiporters. ABA content, extracted by a simplified methodology and estimation by HPLC, is found to be correlated with the degree to which the stress alters plant water status which results in the expression of the identified gene.