We determined uranium in silicate materials such as standard rocks and a meteorite by radiochemical neutron activation analysis. After activation with a cadmium cover, samples were subjected to radiochemical separation of uranium immediately. The gamma-ray intensity of239U was measured with a planar type pure germanium detector system. Our data are mostly consistent with the literature or reported values. Compared with a non-destructive method, the present method was found to improve the sensitivity by at least a factor of ten. Several errors which might be involved in our RNAA procedures were examined and their degrees were evaluated.