A method is presented for determination of 1 p.p.m. or less of uranium in thorium nitrate. Uranium is separated from the latter by ethyl acetate extraction and is determined fluorimetrically, after removing the extracted thorium from the organic phase, by scrubbing it with EDTA-aluminium nitrate solution. The relative standard deviation of the method at 1·00 p.p.m. level of uranium is ±2·7 per cent.