This paper reports an investigation into the suitability of the neutron‐activation method, by use of the reaction238U(n,γ)239U with detection of the gamma‐rays from the daughter239Np, for the determination of uranium in 10 proposed reference materials.182Ta was used to monitor the neutron flux. The precision of measurement varied from 0.92 to 2.7 per cent. Results compare favourably with those obtained by other analytical procedures, and show that this established method can be used to yield useful and independent results in the preparation of uranium reference mater