Electron paramagnetic resonance (EPR) spectroscopy (X- and Q-band) was used for identification of stable radicals in: compact bone powder, shell of arcidae mollusc and crystalline alanine. The aim of our investigation was to analyze the complex EPR spectra of these materials and to identify paramagnetic species contributing to it. The most successful results were obtained in the EPR study (X- and Q-band) on deproteinized and irradiated bone powder and arcidae shell at room temperature