The potential use of potato chips waste as a cheap substrate for lactic acid production by Rhizopus arrhizus NRRL 1526 in a simultaneous saccharification and fermentation was studied. Maximum lactic acid concentration of (17.10g/L) and yield (0.95 g/g starch) were produced when the fungus was cultivated at the determined optimum conditions of medium at pH 6, fermentation temperature 30 ^oC, starch concentration 18g/L, nitrogen concentration 0.4g/L in form of ammonium for cultivation period of 54 hr. Lactic acid used for safe human consumption in the processed meat, poultry industries, salads and confectionery.