A series of new 2-(phenylalkyl)oxirane-2-carboxylic acids has been synthesized and studied for its effects on the concentration of blood glucose. Most of the compounds exhibit remarkable blood glucose lowering activities in fasted rats. Structure-activity studies reveal that substituents like Cl or CF3 on the phenyl ring and a chain length of three to five carbon atoms lead to the most effective substances. Among these compounds, ethyl 2-[5-(4-chlorophenyl)pentyl]oxirane-2-carboxylate (36) exhibits the most favorable activity.