Gamma (ray) spectrometry is a widely used measurement technique in which gamma ray spectra originating from radioactive isotopes are analyzed. The purpose of the experiment is to demonstrate the gamma spectrometry technique by performing gamma spectrum measurements for a selection of radioactive sources. The complex features in the recorded gamma spectra are visualized and their origins explained; radionuclide activities are determined on the basis of the measured spectra, the basic nuclear data and the calibrated detection efficiency.