Hydroxycitric acid (HCA) is a major acid component of the tropical plants Garcinia cambogia and Hibiscus subdariffa. (2S,3S)-HCA from G. cambogia was shown to be a potent inhibitor of ATP citrate lyase (EC4.1.3.8), which catalyzes the extramitochondrial cleavage of citrate to oxaloacetate and acetyl-CoA. (2S,3R)-HCA from H. subdariffa inhibits alpha-amylase and alpha-glucosidase, leading to reduction of carbohydrate metabolism. The availability of HCA is limited by the restricted habitat of the plants as well as the difficulty of stereoselective organic synthesis. Hence, we screened microorganisms producing HCA to find an alternative source of optically pure bulk HCA. Two strains, Streptomyces sp. U121 and Bacillus megaterium G45C, were screened by HPLC analysis. Particular metabolites were purified from their culture broths and compared with authentic HCA from plants. NMR studies indicated that the products are identical to Hibiscus-type HCA. This is the first report showing isolation of microorganisms producing HCA.