We present measured angular distributions for +-elastic scattering at 30 and 50 MeV from selected targets with A=12 to 208. These angular distributions were analyzed using a phenomenological optical potential of first-order form. The mass dependence of the potential strength parameters displays the isospin dependence expected from the free N interaction. NUCLEAR REACTIONS Elastic scattering of 30 and 50 MeV + from C12, O16, Ca40, Zr90, Pb208. Angular distributions: 25°<LAB<160°. Optical model analysis of cross-section data.