The total lipid, protein and glycogen contents of foot, mantle, visceral mass, gonado-digestive gland, gills and adductor muscles of Donax trunculus (Mollusca, bivalvia) from the Gulf of Tunis were analysed during gametogenesis period of the species. Results showed that protein was the major component in the mantle, gills, visceral mass and gonado-digestive gland followed by lipid and glycogen. However, glycogen concentrations in the adductor muscles were greater than those of proteins. The highest levels of lipids, proteins and glycogen were found respectively in gills, foot and adductor muscles which act as reserve organs during gametogenesis.