Measurements of energetic solar flare electrons, Jovian electrons, and low-energy solar protons have led to the suggestion that the inner heliosphere is essentially scatter free. We investigate a model in which scattering is only important within the corotating interaction regions (CIR's), while the cavity formed by the CIR's in the inner heliosphere is scatter free, as compared to an interplanetary diffusion model wherein scattering is determined by the solar wind and magnetic field microstructure everywhere in the heliosphere. The two models are compared in terms of the solar wind stream associated Forbush decreases at 1 AU and the longitudinal cosmic ray nucleonic intensity variations at larger heliocentric distances (Pioneer 11 measurements at ~3 AU). It is shown that the diffusion model is able to explain consistently all longitudinal galactic cosmic ray intensity modulation measurements.