A large fraction of radiation exposure experienced by individuals through ingestion of food, is from natural occurring radionuclides such as K40. In order to find the environmental radioactive background of K40 in Ninevah, Iraq, governorate and its transfer factor from soil to plant and then the effective dose equivalent from milk ingestion, the concentrations of K40 were measured in soil , plant and milk collected from 41 agricultural fields in Ninevah governorate in May/ June 2001.