A novel 1-phenylalkyl-3-phenylurea derivative represented by the following formula (I): ##STR1## wherein R.sup.1 and R.sup.5 represent independently hydrogen, C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.5 alkoxyl or halo; R.sup.2 represents hydrogen or C.sub.1 -C.sub.15 alkyl; R.sup.3 represents C.sub.1 -C.sub.15 alkyl or R.sup.3 represents together with R.sup.2 C.sub.2 -C.sub.9 alkylene; R.sup.4 and R.sup.5 represent independently C.sub.1 -C.sub.5 alkyl, C.sub.1 -C.sub.5 alkoxyl or halo; X represents oxygen or sulfur; Y represents --O--(CH.sub.2).sub.l --O-- wherein l is an integer of 1 to 3 or --(CH.sub.2).sub.p -- wherein p is an integer of 3 to 5; m is 0 or an integer of 1 to 5; and n is 0 or an integer of 1 to 3, is provided. The 1-phenylalkyl-3-phenylurea derivative (I) have the action of reducing cholesterol in blood by ACAT inhibition, and therefore, useful for treating hyperlipemia and atherosclerosis.