Aiming at a synergism of improvements of impact strength of polypropylene by the addition of β-crystal nucleator and of its rigidity by the filling of particulate, the addition of the nucleator to particulate-filled polypropylenes has been studied. 0 to 3000 ppm of γ-quinacridone (GQ) which is a β-crystal nucleator was added to homo isotactic polypropylenes (PP) filled with 0 to 30 wt-% of talc (TC) which shows an α-crystal nucleating effect, of mica (MC), or of glass flake (GF), last two of which show β-crystal nucleating effects. Flexural and Izod impact test specimens were injection-molded from the PPs under constant molding conditions and the structure and properties have been investigated. The β-crystal content is reduced by the filling of particulates. The degree of the reduction is in the order of TC >MC >GF, which agrees with that of the crystallization temperature. The flexural modulus decreases slightly with increasing GQ content and increases with increases in particulate contents. The increase is in the order of MC > TC > GF, which agrees with that of the aspect ratio. The enhancing effect of the Izod impact strength by the addition of GQ decreases with increasing particulate contents and diminishes at contents above 10 wt-%. Particulates deteriorate the enhanced impact strength of β-PP. Thus the expected synergism could not be obtained enough.