Provided are a slurry composition having a low thixotropy and a superior handling property; a cured product of this slurry composition; and a substrate, film and prepreg using such cured product, the substrate, film and prepreg exhibiting excellent mechanical properties and a low relative permittivity and dielectric tangent. The slurry composition has a thixotropic ratio of not higher than 3.0, and comprises: (A) a cyclic imide compound having, per molecule, at least one dimer acid backbone, at least one linear alkylene group having not less than 6 carbon atoms, and at least two cyclic imide groups; (B) spherical silica fine particles and/or alumina fine particles having an average particle size of 0.05 to 20 μm when measured by a laser diffraction method; (C) a silane coupling agent capable of reacting with the components (A) and (B); and (D) an organic solvent.