Low abundance and the labile nature of plant Acetolactate Synthase (ALS) have severely hampered the purification and biochemical characterization of this enzyme. This study was initiated to obtain large amounts of the ALS from pea. We report here the isolation and structural analysis of an ALS gene from a genomic DNA library of Pisum sativum, var. Alaska. Of 10^5 recombinant plaques screened 1 plaque hybridized to Arabidopsis thaliana ALS gene probe. The positive phage DNA was characterized by restriction enzyme mapping and by southern hybridizations. The approximate 4.5 kb EcoRI-SaII fragment carrying presumptive ALS gene was cloned into the plasmid pUC119. From the sequencing of the cloned region, the deduced amino acid sequence of pea ALS showed a significantly high homology with other ALS genes reported so far.