Measurements of radionuclides in urine are widely used to assess the health impact of intakes of radionuclides. The events that followed the polonium poisoning in London in late 2006 have highlighted the need for rapid and reliable methods that can be applied to emergency situations. Ideally such a method would also be applicable to the routine assessment of radionuclides in urine. This paper discusses the development and validation of such a method for measuring the concentration of ²¹⁰Po in urine. The method is validated by assessment of the selectivity, accuracy and recovery, and quantification of the uncertainty. The paper describes two variations of the method, based on whether the priority is a rapid turnaround, or higher sensitivity. The detection limit for the excretion rate of ²¹⁰Po can range from 1.5 to 20 mBq d^–1 depending on the dose limit requirements for different categories of exposure (public, occupational, or emergency).