Publisher Summary This chapter describes the mechanisms responsible for the migration and retention of radioactive contaminants deposited in the inhabited environment, and discusses the dynamic processes that influence dose. These processes also have implications for inhalation doses received from resuspended material, as they determine the amount of contaminant material available for resuspension from the different surfaces. In addition to the “naturally” occurring processes described in this chapter, such factors as anthropogenous mixing, renewal, demolition, and replacement of elements in the environment may play a highly important, though not generically predictable, role in the changes of contamination levels in inhabited areas. A crucial factor in this context is the migration of the contamination on the different surfaces in the environment. Contaminants may penetrate into permeable surfaces that can shield against the radiation, or they can migrate from one surface to another, which may reduce or increase the hazards they pose to people living in the area. The migration depends on the characteristics of the deposited contaminants as well as on the environment in which they are deposited.