Summarized are author's and literary data about the microgravity effects on life span and biological age of animals obtained in experiments with laboratory rats flown in biosatellites Kosmos. Exposure of rats in the spaceflight microgravity as long as 3 wk. (up to 1/50th of the life period of this species) did not reduce the life span post flight. Alterations in biological age as judged by the reproductive function, general resistance and tissue regeneration rate were minor and in a number of parameters were significantly less as compared with the shifts resulting from simulation of the physiological effects of microgravity in laboratory (for a similar period). Prospects of investigations into this problem are considered.