An investigation is made of the importance of (n,,n,–) second-order reaction interferences in reactor neutron activation analysis (NAA), in addition to the commonly considered (n, , –; n, ) interferences. The algorithms for the calculation of the interference are derived from the Bateman-Rubinson equation, taking into account the formation of all m-and g-states involved bum-up effects, and the growth of the interfering radionuclide after irradiation due to a mother-daughter relationship. The following practical cases are examined in detail:138Ba140La (detemination of La in presence of excess Ba),139La141Ce (Ce in La),164Dy166Ho (Ho in Dy),186W188Re (Re in W) and192Os194Ir (Ir in Os). A computer search was done for the nuclear data involved in the computation. For139La[(n,; n,; –)+(n,;–; n,)]141Ce, and164Dy[(n,; n,; –)+ (n,; –; n,)]166Ho experimental checks were performed in the Budapest Research Reactor, which confirmed the calculations showing that the (n,; n,; –) interference gives the largest contribution to the apparent concentration of Ce in La and of Ho in Dy, respectively.