This 3-hydroxydecanoic acid methyl ester is a high purity standard that is useful for the investigation of disorders and diseases. 3-Hydroxy fatty acids are intermediates in fatty acid biosynthesis and have been found to be converted to the omega-fatty acid by the enzyme CYP4F11 and then into dicarboxylic acids in vivo.1 3-Hydroxydecanoic acid is the prevalent fatty acid in the rhamnolipid of Pseudomonas aeruginosa.2 The biologically natural chiral (R)-3-hydroxydecanoic acid is an intermediate in fatty acid biosynthesis. 3-hydroxy fatty acids are used as biomarkers for fatty acid oxidative disorders of both the long- and short-chain 3-hydroxy-acyl-CoA dehydrogenases.3 Polyhydroxyalkenoates of 3-hydroxy fatty acids are polyesters produced by bacteria fermentation and are used for carbon and energy storage. These polyhydroxyalkenoates are of interest in studies regarding the synthesis, properties and mechanisms of bacteria. Short chain-length polyhydroxyalkenoate monomers such as 3-hydroxy fatty acids may have pharmaceutical properties.4,5