A new shearing-interferometry method is used to characterize the basic statistical properties of very rough surfaces of transparent solids. The mean level of these rough surfaces can be curved or flat. Using this method, one evaluates the root-mean-square values (standard deviations) of the heights and slopes of the surface irregularities. Moreover the values of autocorrelation lengths, autocorrelation functions, and one-dimensional height-distribution functions are also determined. The method is applied to a statistical analysis of rough flat or curved glass surfaces. The results from this method agree very well with those obtained with a stylus-type surface instrument and speckle contrast method.