GAMMAN is a toolbox that allows for the efficient automated analysis of large series of gamma spectra, obtained during geophysical surveys. The software contains an implementation of the full spectrum analysis (FSA) method developed by Medusa Radiometrics BV. FSA comprises the mathematically most efficient method to derive nuclide concentrations from gamma ray spectra. The method uses virtually all spectral data present in a gamma spectrum to derive nuclide concentrations.