An extraction - spectrophotometric method is proposed for the determination of trace amounts of uranium in ores, based on its extraction with trioctylphosphine oxide in toluene and development of colour with glyoxal bis(2-hydroxyanil)(GBH) or 1-(2-pyridylazo)naphth-2-ol (PAN) in NN-dimethylformamide in the organic extraction phase without back-extraction. The maximum absorbance with GBH as reagent occurs at 600 nm with a molar absorptivity of 1.48 (± 0.01)× 104 1 mol–1 cm–1 and with PAN as reagent at 555 nm with a molar absorptivity of 2.61 (± 0.02)× 104 1 mol–1 cm–1. Beer's law is obeyed over the ranges 0.6–10.5 and 0.3–6.0 µg ml–1 of uranium(VI)(corresponding to 20–350 and 10–200 µg of uranium in the sample) at 600 and 555 nm, with GBH and PAN, respectively. The proposed method has been applied successfully to the analysis of standard and synthetic uranium ores with uranium contents of up to 0.15%.