Oxo-biodegradation of polyethylene has been well studied with different pro-oxidants and it has been shown that pro-oxidants have limited role in the oxidation of polyethylene and do not have any role in microbial growth. However, in few recent studies, montmorillonite clay has been reported to promote the growth of microbes by keeping the pH of the environment at levels conducive to growth. In an attempt to improve the overall oxo-biodegradation of polyethylene, montmorillonite nanoclay has been used in this study along with a prooxidant. Film samples of oxo-biodegradable polyethylene (OPE) and oxo-biodegradable polyethylene nanocomposite (OPENac) were subjected to abiotic oxidation followed by microbial degradation using microorganism Pseudomonas aeruginosa. The progress of degradation was followed by monitoring the chemical changes of the samples using high-temperature gel permeation chromatography (GPC) and infrared spectroscopy (FTIR). The growth of bacteria on the surface of the polymer was monitored using environmental scanning electron microscopy. GPC data and FTIR results have shown that the abiotic oxidation of polyethylene is influenced significantly by the pro-oxidant but not by nanoclay. But, the changes in molecular weight distribution and FTIR spectra for the biodegraded samples indicate that the growth rate of P. aeruginosa on OPENac is significantly greater than that on OPE. It indicates that nanoclay, by providing a favourable environment, helps in the growth of the microorganism and its utilisation of the polymer surface and the bulk of the polymer volume. (C) 2006 Wiley Periodicals, Inc. J Appl Polym Sci 113: 2826-2832, 2009