Abstract: A method for re-fracturing of wells having perforated casing that were previously fractured is provided. The method employs degradable ball sealers having a density near that of the injection fluid such that high seating efficiency of balls on perforations is attained. The balls degrade at varying rates, so that some intervals are opened for fracturing while other intervals are still blocked by ball sealers. After fracturing of an interval, the interval may by shut-off by ball sealers that degrade at a much slower rate or that do not degrade. The method may be applied to proppant fracturing or acid fracturing.