Various composites of polypropylene (PP) produced using natural fibers such as pineapple leaf fiber, banana fiber, and bamboo fiber were studied for their degree and rate of aerobic biodegradation. Composites used contained 10, 15, and 50% volume fractions of pineapple leaf fiber, banana fiber, and bamboo fiber, respectively, which are the optimum fiber percentages of the respective composites as reported by these authors in their previous works. Cellulose has been used as positive reference material. All the composites exhibited partial biodegradation in the range of 5-15% depending on the fiber content. Degradation had not taken place in the covalent ester linkages between the natural fiber and the MA-g-PP compatibilizer but in those areas of the fibers which have remained only physically embedded in the resin matrix. Thus, although natural fibers reinforced PP composites are not excellent biodegradable material, they can address to the management of waste plastics by reducing the amount of polymer content used that in turn will reduce the generation of nonbiodegradable polymeric wastes. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 2226-2232, 2011