An experimental study of the blow molding of talc-polyethylene and talc-polypropylene compounds is presented. These compounds are found not to exhibit-zero shear viscosity but rather yield stresses, below which there is no flow. The annular swell of the compositions is greatly reduced compared to the neat thermoplastics, but extrusion sag is minimized. Blow molded bottles of talc-thermoplastic compounds were found to have much greater thickness uniformity than blow molded neat polyolefins. The talc particles were determined, by X-ray diffraction, to be oriented with the flake surfaces parallel to the mold surface or equivalently to the bottle surface.