Proton induced X-ray emission (PIXE) technique [1, 2] relies on the analysis of the energy spectra of characteristic X-rays emitted from a sample bombarded with 1-3 MeV protons. The major advantage of the PIXE technique is a low background yielding high sensitivity for trace element determination. Since the proton limited range and the absorption of the X-ray photons in the sample material, only several micrometer thick outer layer is analysed and the total amount of the analysed material commonly varies from micrograms to miligrams. In our PIXE facility the samples kept in a vacuum chamber are irradiated with 2.5 MeV proton beam and the characteristic X-ray spectra are registered with a Si(Li) semiconductor detector coupled to standard electronics and a PC based multichannel analyser. The PIXE spectra are evaluated by the PIXE-INP code developed in our laboratory. The elements from Al to U can in principle be determined with the detection limits above 1 ppm. At Nuclear Physics Institute the PIXE technique can be combined with other analytical techniques, such as RBS or Neutron activation analysis. The most extensive use of the PIXE method is in elemental analyses of atmospheric aerosol samples, dust and fly-ash samples, different biological materials, archeological and artistic artefacts ect.