Microbial Stereoselective hydrolysis of (±)-cis, trans-ethyl chrysanthemate was examined to prepare (+)-trans-chrysanthemic acid. Through the screening of over 228 strains from culture collections, 31 strains were found to have hydrolytic ability. Stereoselective hydrolysis by Arthrobacter (A.) globiformis IFO-12958 gave the optically pure (+)-trans-aciA. The composition of cultivation media for production of the hydrolytic activity (the responsible esterase) was optimized. The optimum pH and temperature for hydrolysis of ethyl chrysanthemate were pH 10 and 55°C, respectively. Cells of A. globiformis IFO-12958 were treated with a chemical mutagen and the advantageous mutant SC-6-98-28, the hydrolytic activity of which was enhanced 2.5-fold, was isolated.