The method prosposed uses arsenazo Ⅲ as indicator for photometric titration of microgram quantities of rare earths with EDTA.The optimum pH range for the titration is 4.5-6.4.Under this condition, arsenazo Ⅲ forms a green complex giving a maximum absorbance at 660 mμ.An exact value for extinction at the equivalence point has been calculated with the Ringbom's equation.The influence of various factors on the titration is discussed.For amounts of lanthanum, gadolinium, terbium, ytterbium and yttrium varying from 3 to 9μg, the method gives satisfactory results.The method is also applicable to the determination of total rare earths.