The invention provides novel (2S)-2-ethylphenylpropanoic acid derivatives that bind to the receptor as ligands of human peroxisome proliferator-activated receptor (PPAR) .alpha. to activate and exhibit lipid-lowering effect, inhibitory effect on the arteriosclerosis, antiobesity effect, blood glucose-lowering effect, etc., their addition salts, and their medicinal compositions.(2S)-2-Ethylphenylpropanoic acid derivatives represented by a general formula (1) ##STR00001## [wherein R1 denotes a halogen atom or trifluoromethyl group, R2 denotes a hydrogen atom, halogen atom or trifluoromethyl group, and, when R2 denotes a hydrogen atom, R3 denotes a halogen atom or trifluoromethyl group and, when R2 denotes a halogen atom or trifluoromethyl group, R3 denotes a hydrogen atom, halogen atom or trifluoromethyl group], and their addition salts.