Measurements have been made of the fast neutron cross sections for the production of N16 and N17 in the uranium rod cooling water of the NRX reactor by the reactions O16(np)N16 and O17(np)N17. The N16 and N17 were detected by their gamma and fast neutron activities, respectively, in a continuously flowing sample of the effluent water from a uranium rod. The cross sections (fission neutron spectrum) for the reactions O16(np)N16 and O17(np)N17 are 1.85 ± 0.15×10-2 millibarns and 9.3 ± 0.9×10-3 millibarns, respectively.