A peroxisome proliferator activated receptor regulator containing a carboxylic acid derivative of formula (I) ##STR1## (wherein all symbols are as defined in the specification), a non-toxic acid thereof or a hydrate thereof as active ingredient. Because of having an effect of regulating PPAR, a compound of formula (I) is useful as a hypoglycemic agent, a hypolipidemic agent, a preventive and/or a remedy for diseases associating metabolic disorders (diabetes, obesity, syndrome X, hypercholesterolemia, hyperlipoproteinemia, etc.), hyperlipemia, atherosclerosis, hypertension, circulatory diseases, overeating, coronary heart diseases, etc., an HDL cholesterol-elevating agent, an LDL cholesterol and/or VLDL cholesterol-lowering agent and a drug for relief from risk factors of diabetes or syndrome X.