Reaction of isatoic anhydride with aniline derivatives gave 2-amino-N-(aryl)benzamides. The latters reacted with phenyli-sothiocyanate in the presence of heteropolyacids in various solvents which afforded 3-(aryl)-2-thioxo-2,3-dihydroquinazolin-4(1H)-one derivatives. The effects of various heteropolyacids including Preyssler and Keggin on the yields and reaction times have been investigated.