NEW MATERIAL:A 3-phenyl-4-quinazolone derivative of formula I (R1,2 are lower alkyl; R3 is alkyl; R4,5 are H, halogen, alkyl, or alkoxy; R6 is H, halogen, alkyl, alkoxy, trifluoromethyl, nitro, or R4 and R5 together form methylenedioxy group).

EXAMPLE: 6-Ethoxycarbonyl-5,7-dimethyl-3-phenyl-4-quinazolone.

USE: Drug having anti-thromboxane activity and blood vessel smooth muscle relaxation activity, and effective for the prevention and remedy of ischemic cerebral vascular lesion, ischemic cardiopathy and thrombosis, as well as drug having blonco-dilating activity.

PROCESS: The compound I is prepared by reacting 1mol of a compound II (R is H or lower alkyl) with 1W1.2mol of a compound III at 150W250°C, pref. about 200°C.