Objectives: Parasitic infestations of livestock are a threat for the meat resources as well as a trouble to health of the consumers. Given the geographical situation of Mazandaran, tribal living and animal farming systems in this region, prevalence of zoonosis is probably high. Fasciola hepatica is an important parasite of sheep, goats and cattle and has been the subject of many scientific investigations. The present study was done in order to investigate the infestation rate of slaughtered cattle in Mazandaran slaughterhouses. Materials & Methods: This descriptive study was carried out prospectively concerning the slaughter chart of the year 2009 available in Mazandaran industrial slaughterhouses. The information present in the charts was transferred to the tables designed according to desired variables such as the number of the slaughtered cattle, the kind of parasite, the number of the infested domestic animals, month and season. The data was analyzed statistically by SPSS. Results & Conclusion: In this study, the prevalence of Fasciola hepatica was investigated and it was concluded that 2602 cattle out of the total number 86963 slaughtered cattle were infested by this parasite. Infestation rate was (2.99%). In general, the highest prevalence rate season and month was autumn and October respectively. The infestation rate for zoonosis is considerable in Mazandaran. Separation of the infested domestic animals, omission of infested carcasses from the food cycle as well as treating infested animals can play an important role in improving the public health. Infestations occurred mostly in autumn and it is thought, given the life cycle of parasites that these infestations occur due to contamination of animals in spring and summer. Strategies used to control fasciolosis mostly depend on the extent and seasonality of disease transmission, the intermediate host���s ability to survive climatic conditions and husbandry practices of domestic farmers.