We have proposed a new route to produce 99Mo for nuclear medicine by the 100Mo(n,2n)99Mo reaction. The reaction cross section is known to be ∼1.5 b in the neutron energy, En, range from 12 to 17 MeV: 10-times larger than the thermal-neutron capture cross section of 98Mo. By irradiating an enriched 100Mo target for 198 h with neutrons of ∼1013 n/(cm2 s) at En∼ 14 MeV, one can produce 79 GBq/g specific activity of 99Mo. Since the cross sections for 100Mo(n, p)100Nb, 100Mo(n,n p)99Nb and 100Mo(n,α)97Zr at 12≤ En≤ 17 MeV are small, less than a few mb, radioactive waste during and/or after chemical processing of 99Mo would not be a serious problem. The proposed route could bring a major breakthrough in the solution of ensuring a constant and reliable supply of 99Mo without using highly enriched 235U.