New azaphilones named isochromophilones III-VI were isolated from the culture broth of Penicillium multicolor FO-3216 as inhibitors of acyl-CoA: cholesterol acyltransferase (ACAT). Their structures were elucidated by NMR and other spectroscopic analyses. The IC50 values of isochromophilones III, IV, V and VI for ACAT activity in an enzyme assay using rat liver microsomes were calculated to be 110, 50, 50 and 120 microM, respectively.