To investigate the status of conventional laboratory mice colonies for zoonotic bacteria, three mice colonies, NIH, NMRI and Balb/c strains of Razi institute were studied for five zoonotic bacteria including Pasteurella pneumotropica, Salmonella typhimurium, Salmonella enteritidis, Streptobacillus moniliformis, Streptococcus Pneumonia. Study populations were 74 mice of premature, mature and post mature ages. Same numbers of male and female animals were allocated in a random fashion from each 3 strains of mice. Two hundred and ninety six specimens of nasopharynx (n=156)),cecum (n=70) and liver (n=70) were taken from 74 animals and cultured for bacteriological tests. Results showed that none of tested specimens, infected by mentioned zoonotic bacteria, however in 78% (231/296) of mice, commonly nonpathogenic bacteria, mainly Escherichia coli, Bacillus sp, Streptococcus other than Streptobacillus moniliformis, and Entrobacter aerogenes were observed. The results of study recommend use of these animals have no human risk or research interferences for mentioned zoonotic bacteria. However like other conventional laboratory animals, precaution and personnel's safeties must be considered while using in researches where the existing bacteria may interfere the results.