A study of the fluorescence system of the Eu3+-2-benzoyl-indan-1,3-dione-trioctylphosphine oxide-Triton X-100 was made. The excitation and emission wavelengths were 348 and 612 nm, respectively. The fluorescence intensity was a linear function of the concentration of europium in the range 1.0×10−8- 1.0×10−6mol/L. The detection limit was 4.0×10−9mol/L. The standard addition method was used for the determination of europium in rare earth oxides, with satisfactory results.