More than ever before, thermoplastic polyolefin (TPO) is actively used for interior and exterior applications in the automotive industry. Foamed TPO parts use far less material than their solid counterparts and, thereby, reduce material cost, weight, and fuel usage. However, foamed TPO is not yet in mainstream use because the appropriate foaming technology is not yet well developed. The literature reports the use of carbon dioxide (CO2) as a blowing agent for TPO;(1-3) there is, however, little research on the use of nitrogen (N-2) as a blowing agent, despite nitrogen's numerous advantages. In this study, various talc contents were added to a TPO matrix consisting of polypropylene blended with a metallocene-based polyolefin elastomer. The effect of talc on the TPO foams blown with N-2 was studied with a batch foaming simulation system. The simulated results were compared actual foam extrusion results. The influence of the N-2 content and processing conditions on the cell nucleation behavior is discussed. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 1691-1703, 2010