A new nuclear excitation process,99Tc (, )99mTc reaction, was applied for the first time to radioactivation analysis of technetium. Bremsstrahlung irradiation of99Tc samples gave the reaction product99mTc which emits -ray measurable with ease by a semiconductor detector. The production rate of99mTc per g99Tc was linearly correlated with the flux of bremsstrahlung. The detection limit of99Tc was estimated to be nanogram order (0.63 Bq99Tc) under the optimum irradiation condition. Possible interference by100Ru(, p)99mTc reaction was also studied, which could be discriminated from the (, ) reaction by simultaneously occurring98Ru (, p)97Ru reaction.