Hygienic characteristics of fresh dairy products with a short period of preservation are taking up at present far more importance. In the case of cheeses made from pasteurized milk the final hygienic quality is strongly influenced by secondary contaminations occurring during the technological process of production. A previous research allowed to recognize possible points of contamination in the processing phases between salting in brine and packaging. The present work evaluates the effect of secondary contaminations on the length of the preservation period through microbiological determinations on cow's milk Mozzarella cheese packaged in different ways. The samples were partly hand wrapped up with the procedure currently adopted by the dairy plant (A) and partly drawn aseptically soon after cutting off, salted in sterile brine and wrapped up wearing sterile mask and gloves (B). All the samples came from the same processing cycle. Half the samples of groups A and B were stored at 4 degrees C and the rest was kept at 20 degrees C. The analysis at 0, 2, 4 and 7 days gave different values of microbial counts for each series of samples. Test B stored at 4 degrees C showed every time lower numbers of microorganisms for all the microbial groups taken into account, thus pointing out a method in perfect agreement with a longer shelf-life of the product.