A new analytical technique using inductively coupled plasma--quadrupole mass spectrometry (ICP-QMS) has been developed that produces permil-level precision in the measurement of uranium concentration () and isotopic composition (δ234U) in natural materials. A 233U-236U double spike method was used to correct for mass fractionation during analysis. To correct for ratio drifting, samples were bracketed by uranium standard measurements. A sensitivity of 6--7 ¿ 108 cps/ppm was generated with a sample solution uptake rate of 30 ¿L/min. With a measurement time of 15--20 min, standards of 30-ng uranium produced a within-run precision better than 3? (¿2 R.S.D.) for δ234U and better than 2? for . Replicate measurements made on standards show that a between-run reproducibility of 3.5? for δ234U and 2? for can be achieved. ICP-QMS data of δ234U and in seawater, coral, and speleothem materials are consistent with the data measured by other ICP-MS and TIMS techniques. Advantages of the ICP-QMS method include low cost, easy maintenance, simple instrumental operation, and few sample preparation steps. Sample size requirements are small, such as 10--14 mg of coral material. The results demonstrate that this technique can be applied to natural samples with various matrices.