The concept of the Biostack experiment has become practicable through European scientific collaboration and with help of NASA. The objectives of this experiment flown aboard Apollo 16 and 17 are to study the biological effects of individual heavy cosmic particles of high-energy loss (HZE) not available on earth; to study the influence of additional spaceflight factors; to get some knowledge on the mechanism by which HZE particles damage biological materials; to get information on the spectrum of charge and energy of the cosmic ions in the spacecraft; to estimate the radiation hazards for man in space. For this purpose the Biostack experiment comprises a widespread spectrum of biological objects, and various radiobiological end-points are under investigation. Bacterial spores, protozoa cysts, plant seeds, shrimp eggs, and insect eggs were included in the Biostack experiment packages together with different physical radiation detectors (nuclear emulsions, plastics, AgCl crystals, and LiF thermoluminescence dosimeters). By using special arrangements of biological objects and physical track detectors, individual evaluation of tracks was obtained allowing the identification of each penetrating particle in relation to the possible biological effects on its path. The response of the different biological objects to space flight and HZE ions bombardment was of different degree, presumably depending on the ability of the organism to replace the cells damaged by a hit. The results help to estimate the radiation hazard for astronauts during space missions of long duration.