Statistical properties of plastically roughened metallic surfaces are studied together with the relation between the angular distribution of the reflected-plus-scattered intensity from such a surface and the plastic deformation it has experienced. The height probability density distribution ofthe plastically roughened surfaces is shown to be Gaussian. The surface autocorrelation function is neither Gaussian nor exponential, even though the former fits the experimental data better. The combination of a scalar scattering theory and the plasticity-induced surface roughening empirical relations yields some new expressions. These expressions relate scattered light with plastic deformation for surfaces with Gaussian or exponential autocorrelation. The applicability, convergence, and limitation of the thus obtained expressions are also studied. A theoretical-numerical analysis provides background to some existing strain measuring methods, such as the maximum intensity, half width, and correlation coefficients. The present approach is verified favorably by some experiments on aluminum alloys and is in support of the experimental results in literature.