The initial rates of resistivity increase in platinum specimens with many different concentrations of vacancies injected by quenches are measured during electron irradiations at temperatures between 80 and 200 K. The ratio of the initial rate in a quenched specimen to that in a specimen well annealed before irradiation decreases with increasing vacancy concentration; but these ratios are nearly independent of irradiation temperature over this range. Thermal conversion of interstitials in platinum is negligible below 200 K.