A procedure is described for microwave mineralization of urine or faeces samples as replacement for wet mineralization. The new method uses a sodium peroxosulfate solution at pressures lower than 4 MPa in two consecutive mineralizations for 60 and 30 s. For complete decomposition, it is necessary to boil the mixture once again with a sodium peroxosulfate solution and evaporate it to dryness. The results obtained are about 5-10 % higher than those from classic mineralization, which indicates a more thorough decomposition of the matrix. The time required for microwave mineralization (ca. 30 min) is substantially shorter than that for wet mineralization. The same method can be used in determination of metals in urine simultaneously (e.g. cadmium, thallium, copper, and lead).