The growth of pathogenic and spoilage strains in saturated milk or whey with carbon dioxide (CO2) was studied. In saturated milk, the highest log reductions were 2.0 and 1.3 for Staphylococcus aureus and Candida albicans. After two weeks of cold storage, the log reductions were reached to 2.9, 2.48 and 2.0 for Candida albicans, Staphylococcus aureus and Pseudomonas aeruginosa, respectively. Slightly inhibitory effect could be detected with some strains in saturated whey. The highest log reductions 0.2 was reported for Pseudomonas aeruginosa after cold stored of whey for two weeks. The log reduction of Staphylococcus aureus was 0.36 in milk with pH 5.5. In milk with pH 6.6, the log reductions were 2.0, 1.3 and 0.5 for Staphylococcus aureus, Candida albicans and Bacillus cereus, respectively. CO2 addition was showed a good log reduction for Candida albicans, Staphylococcus aureus and Pseudomonas aeruginosa in milk with cold storage and pH 6.6. So, the addition of carbon dioxide was more effective against pathogenic strains in saturated milk than in whey. Also, the effect of CO2 was independence according to strain type. Therefore, we can use dissolved carbon dioxide to reduce the microbial load and extend the shelf life of dairy products.