The inhibition of cell recovery might be proceeded via either the damage of the mechanism of the recovery itself or via the formation of irreversible damage which could not be repaired at all. Both these processes may take place at the same time. Any of these possibilities would result in a decrease in both the rate and extent of cell recovery. To distinguish them, a quantitative approach describing the process of recovery as a decrease in the effective radiation dose was applied to experimental data on the recovery from potentially lethal damage in Chinese hamster cells exposed to X-rays alone or combined with various chemicals (pyruvate, novobiocin, lactate, nalidixic acid, 3-aminobenzamide). For these particular cases, it is concluded that the recovery process itself is not damaged and the inhibition of the recovery is entirely due to the enhanced yield of the irreversibly damaged cells.