By exploiting the simplicity of a novel transport measurement on a ferromagnetic striped domain structure in a thin film of cobalt, we report the first direct observation of ferromagnetic domain wall scattering and what we believe to be the first clear indication of giant magnetoresistive effects in a homogeneous magnetic system. (The colossal MR effect, while seen in homogeneous materials, is believed to originate from a charge ordering phenomenon [see, for example, Y. Tokura et al., J. Appl. Phys. 79, 5288 (1996), and references therein], and is therefore distinct from GMR, which is an effect arising from spin dependent scattering. ) A new model is proposed to describe these observations which highlights the crucial role played by electron spin precession in determining the electrical transport properties of magnetic interfaces.