Enriched 33 S, prepared by electromagnetic separation techniques, and 36 Cl, prepared by reactor irradiation of natural chlorine, were evaluated as targets for the production of 33 P by the 33 S(n,p)33 P and 36 Cl(n,α)33 P reactions. The fission-neutron cross sections of these reactions and those of the 32 S(n,p)32 P and 35 Cl(n,α)32 P reactions were measured in four positions in the Oak Ridge Research Reactor (ORR) at various distances from the fuel elements. Millicurie quantities of 33 P were prepared by fast-neutron irradiation of enriched 33 S and 36 Cl and subsequent aging to deplete the 32 P content of the 33 P. Chemical procedures for separation of carrier-free phosphorus activities from elemental sulfur and NaCl are given.