We have prepared a series of novel gelatin derivatives through reactions of gelatin with alkyl succinic anhydride and polyoxyethylene stearyl ether. These derivatives contain gelatin units and polyoxyethylene chains as their hydrophilic moieties and alkyl succinic anhydrides and 18-carbon-atom alkyl chains as their hydrophobic moieties. Surface activities were evaluated in terms of the materials' surface tensions, wetting abilities, emulsifying powers, and foaming properties. The surface tensions were characterized with respect to the critical micelle concentration (cmc), the surface tension at the cmc, the maximum surface excess concentration, the standard free energy, and the surface area per molecule at the air-water interface. The modified gelatins were more surface-active relative to gelatin itself. Increasing the polyoxyethylene chain length led to a decrease in surface activity. The excellent foaming, wetting, and emulsifying behavior of the gelatin derivatives was a direct result of the presence of their multiple hydrophilic and hydrophobic units. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121:2993-3000, 2011