The degradation of a number of cellulose acetate/nitrate-based 35mm cinematograph films has been studied by moisture regain, UV absorption, viscometry, pH, and degree of insolubilization. Analysis of naturally aged films indicates a correlation between moisture regain, acidity, and degree of degradation. Artificial aging studies at various temperatures and at different humidities show that temperature, moisture regain, and pH are important related factors in the degradation mechanism. The results show conclusively that the degradation of ester-based film is associated with an acid-catalyzed hydrolysis of the ester group resulting in a consequent reduction in the molecular weight of the polymer. It is also indicated that there is a minimum concentration of acid necessary to produce hydrolysis and that above this threshold the less moisture present in the environment the more rapid the rate of degradation. The results therefore call into question current standards for storage of ester-base motion-picture films and suggest stabilization as an alternative means of preservation.