Studies on solvent extraction of uranium(VI) by a commercially available chelating extractant LIX-54 (a -diketone derivative) (HA) and its mixtures with tri-n-butyl phosphate (TBP) in benzene diluent show quantitative extraction by a mixture of 5% LIX-54 and 5% TBP at pH 4.3. Influence of different proportions of LIX-54 or TBP in the mixtures on the extraction of the same metal ion has been studied. Pronounced synergism has been observed. The composition of the extracted species seems to be [UO2(OH)(A)(HA)(TBP)] as determined from slope analysis. Slopes of the linear plots were computed employing regression analysis and variance in results has been shown.