Black poplar mushroom, Agrocybe cylindracea deserves special attention, due to its medicinal properties. Water and alcohol extracts from fruiting bodies of the fungus have an anti-oxidant, anti-cancer, anti-fungal, cholesterol and triglycerides blood level lowering abilities. This mushroom is rich in proteins and vitamins, mineral elements and low in fat. The aim of the experiments was to determine effect of a substrate supplementation with CaCO 3 on mycelial growth, yield, morphological features and storability of fruiting bodies of four strains of A. cylindracea (DC.) Marie. The amount of additive to sawdust substrate affects rate of mycelial growth and yield of investigated strains. A. cylindracea mycelial growth was not affected by addition of CaCO 3 to substrate, however a significant effect of this additive was found on yield, which was the highest with CaCO 3 addition in an amount of 8 g/100 g of substrate. Carpophores characterized with the largest caps diameter, and the largest individual mass obtained of substrate enriched with CaCO 3 addition of 8 g/100 g of substrate. In addition, it was found that supplementation with CaCO 3 affect storability of A. cylindracea . The lowest weight loss of fruiting bodies after 3 and 7 days of storage was found with addition of CaCO 3 to substrate in an amount of 4 g/100 g of substrate.