The distribution of irradiation-produced defects in thin foils of steel and aluminium is calculated using Brailsford and Bullough's rate theory of swelling plus appropriate boundary conditions. The dependence of the void denuded zone on temperature, dose, radiation damage rate and sink strength is studied. The width of this zone is found to be inversely proportional to the sink strength and damage rate. For a uniform initial distribution of loops and void embryos the loop denuded zone is much smaller than the void denuded zone. Also, a swelling enhancement adjacent to the void denuded zone is predicted under some initial conditions.