A detailed study of the kinematics of neutron-proton, proton-neutron and neutron-neutron scattering (henceforth calledn-p,p-nandn-nscattering, respectively) reveals a significant difference in the elastic differential cross section in laboratory directions corresponding to the near backward direction in the center of mass system. Based on the finiten-pmass difference, then-pscattering cross section goes to ∞ at 86°59.5′, thep-nscattering shows a slight amount of backward scattering and then-nscattering cross section equals zero for all laboratory angles greater than 90°. Most treatments ofn-pscattering limit the discussion of the kinematics of the scattering process to a neutron-proton mass ratio to unity. It is of interest to consider the extent to which the actual difference in mass influences the angular distribution of the scattered particle. It is the purpose of this paper to discuss the consequences of the small, but non-negligible,n-pmass difference in the kinematics of scattering. Although it is not possible to obtain free neutrons at rest and hencep-nscattering cannot be observed in the laboratory, it, withn-nscattering is discussed here to get an idea as to what the kinematics ofn-pscattering would have been if neutrons were lighter than protons and if the neutron mass were exactly equal to the proton mass.