Procedure for direct determination of uranium in urine by ICP-MS.Estimation of the internal exposure of personnel by radioactive substances, especially actinides, is one of the subjects of great importance in human radiological protection. Because of constant changes in industrial processes in the nuclear fuel cycle and new radiological protection regulations, means to perform routine individual monitoring and to estimate internal exposure of workers in an accident situation must be high-efficient. The method described here is the determination of uranium in urine by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry), directly after a simple 20-fold dilution of the urine samples. Optimisation of the operational parameters has led to propose an analytical procedure that allows the determination of mass concentration for each uranium isotope. Calculations of associated uncertainties and corresponding detection limits are detailed.