About the Project "MARS - 500" Realization of manned flight to Mars requires solving of many problems. The main among them is the problem of biomedical support of the crew owing to the highest priority of the human factor. The point is that a human is the most important element, to a great extent determining the possibility of successful realization of the mission. At the same time he is the most vulnerable unit in the system "crew-spaceship" because of his susceptibility to influence of the flight negative factors. For refinement of the strategy and substantiation of realization ways of the Martian expedition biomedical support it is necessary to conduct anticipating investigations in manned orbital flights, on automatic space vehicles and in ground-based simulation experiments. At the State Scientific Center of the Russian Federation - Institute of Biomedical Problems of the Russian Academy of Sciences (SSC RF - IBMP RAS) in the IV quarter of 2007 it is planned to begin ground-based experiment with the duration of 520 days (with the possibility of extension up to 700 days) simulating manned flight to Mars. As a result of the experiment the data will be obtained to refine the conception of the Martian manned mission biomedical support, as well as to formulate initial requirements to the flight conception in general, to the constituent parts of the Martian Expeditionary Complex and to the crew's life support systems.