Particle induced X-ray emission (PIXE) technique was employed for analysis of trace elements in two biological standard reference materials: Bovine Liver (1577c) and Animal Blood (A-13) prepared by National Institute of Standards and Technology (NIST), USA and International Atomic Energy Agency (IAEA), Vienna respectively. The PIXE experiments were carried out by using 3 MV Tandem Pelletron Accelerator facility at Ion Beam Laboratory (IBL), Institute of Physics (IOP), Bhubaneswar, India. A proton beam of 3 MeV energy was used to excite the samples under study. The concentrations of the elements obtained in the reference materials were compared with the certified values of NIST and IAEA. The determined values were 88-125% relative to NIST and IAEA certified values except for Mn in the Animal Blood sample.