The light‐induced decrease of the photoconductivity in deuterated amorphous silicon is a factor of 3 less even though the defect density increase is greater than in hydrogenated material having equivalent as‐deposited properties. Consequent changes in the average recombination cross section of the defects is illustrated. Since the differences in the light soaking behavior upon isotopic substitution has been found to disappear in films deposited at low temperatures, the changes are thought to arise from differences in the silicon network occurring during growth.