Radiobiological techniques may be used for determining the size of a population of cells capable of indefinite proliferation (clonogenic cells). In normal “steady‐state” proliferative tissues, such as intestinal mucosa, clonogenic cell numbers remain constant through the continuous loss of cells. In order for a depleted clonogenic population to regrow to normal, cell loss must be reduced temporarily. The time‐sequence for the switching off and on of cell loss from the intestinal mucosa is reported here and could form a temporal framework for more detailed studies of the mechanisms that control cell loss, and therefore growth.