Background: Milk is a valuable source of nutrients that microorganisms can grow in favorable conditions on it. This study was conducted to evaluate the microbiological quality of pasteurized and sterilized marketing milks in Bushehr. Material and Methods: This descriptive study was conducted in the autumn and early winter 2011. In this study 11 brands including 6 pasteurized, 5 sterilized brands and in total 160 samples were elevauted. Microbial tests included heterotrophic bacteria (HPC), total coliform and Escherichia coli (E.coli) were conducted according to standard methods. Results: results of this study showed that from 98 pasteurized samples, 35/7% and HPC and 15/2% of samples were contaminated by HPC and total coliform, respectively. There was no microbial contamination in all 62 sterilized samples. Mean heterotrophic bacteria in pasteurized milk was much more than Iranian national standard. Conclusion: In this research the relationship between heterotrophic and coliform bacterial growth with temperature and time variation between production date and sampling date (maintenance period) were measured and the results showed that bacterial growth had direct and significant association with temperature but there was no statistically significant association with maintenance period.