PURPOSE: To treat atherosclerosis by using a N-phenylthiourea deriv. or its isolated form or salt.

CONSTITUTION: A pharmaceutical compsn. containing a compd. expressed by formula I is effective for prophylaxis and treatment for atherosclerosis. In formula I, R1 is H, 1 to 22C alkyl, 3 to 6C cycloalkyl, etc.; R2 is H or -NR1R2 is pyrrolidino, N'-alkyl-piperadino, etc.; R3 is H, 1 to 3C alkyl; R4 is H, 1 to 4C alkyl, 1 to 3C alkyl; R5 is H, 1 to 4C alkyl, halogen, etc.; R6 is H, 1 to 3C alkyl, etc. The compd. of formula I is, for example, N-(5-chloro-2- methylphenyl)-N'-propylthiourea. The compd. of formula I is obtd. by allowing an isothiocyanate expressed by formula II to react with an amine expressed by R1R2NH in a solvent such as methylene chloride at 10 to 40°C.