Background and Aims: Adventitious agents, especially viral agents are among the most important concerns in viral vaccines. Viral contamination of biological products may arise from the original source of the reagents such as, serum, trypsin, animal or human derived media components or cell culture and working seed or cross contamination of vaccine during production. In this study, adventitious agents were evaluated in the MMR and oral polio vaccines. Methods: For detection of adventitious agents, two techniques were used. The suspensions that were harvested after inoculation on MRC-5 were neutralized with specific antisera and inoculated into Vero, HeLa and MRC-5 cells (in vitro tests). The suspensions that harvested after inoculation of CHEF primary cell culture were neutralized with specific antisera and inoculated in to Vero, MRC-5, CHEF, chorioallantoic membrane and yolk sac of SPF embryonated eggs (in vivo tests). Results: As indications of viral contamination, CPE in cell culture and the viability of egg embryo were observed and haemadsorption and haemagglutination test were performed. Finally, data were analyzed by exact binomial test (version 2.8.1). There was not any CPE in cell culture, the inoculated embryos were viable and there was not any haemadsorption & haemagglutination in all of the samples. Conclusion: The major focus of this Study will be to ensure that vaccines are devoid of adventitious agents. There were not any signs of viral agents in the samples and the preparations could be used for vaccine production.