Cyanobacteria are photosynthetic organisms. This study aimed to examine the cellular tolerance of a terrestrial cyanobacterium, Nostoc sp. HK-01 to cosmic rays to assess its potential application in studies on extraterrestrial environments and the possibility of interplanetary transformation. This strain is a candidate organism for introduction in extraterrestrial environments such as those on Mars owing to its high tolerance to heat, dryness, and vacuum conditions. Dried cells were exposed to extreme environments and survival germinated cell rates were conformed after the tests. Dried cells of Nostoc sp. HK-01 colonies were exposed to a temperature cycle of 80 degrees C and - 80 degrees C for 90 min, vacuum, a helium-ion beam (He), ultraviolet (VUV) rays (172 nm), UV rays (254 nm), and gamma rays (5 kGy). Live cells were confirmed in all experiments. The D-10 values of a helium-ion beam, VUV, UV and a gamma rays (5 kGy) tests were 2.9 kGy, 11.5 kJ cm(-2), 1.2 kJ cm(-2) and 19.9 kGy, respectively. The present results indicate that cyanobacteria can be potentially used for future manned space missions and it was confirmed that these cells could be transported to extraterrestrial environments.