In this study, the effects of antimicrobial agent (natamycin) and packaging materials (PVC, Sperdex-Ref. 99017) on the microbiological properties of Kashar cheese during ripening period were investigated. Natamycin and packaging materials had no effect on the total aerobic mesophilic bacteria, yeast and lipolytic, microorganism counts. However, natamycin had showed inhibitory effect on the proteolytic microorganisms by itself and combined with packaging material, Sperdex-Ref. 99017. In addition, no mould growth were detected in the Kashar cheese samples produced by combined application of natamycin and packaging materials during five month ripening period. Enterobactericeae, Coliform, Salmonella spp., and Staphylococcus aureus were not found any of the cheese samples. (c) 2004 Published by Elsevier Ltd.