The Ponzo and Muller-Lyer illusions were presented to two groups of volunteers during 8 days (2 days prior "dry" immersion, during 5-day immersion, one day after its end). The volunteers of the IM+L group put on a suit "Penguin" providing axial load every day of immersion, the volunteers of the IM group were not exposed to any influences other than immersion. We found the differences in verbal and sensorimotor estimations of two illusions in these groups. It was shown that according to verbal response there was the linear decrease of the strength of illusions during the experiment; at the sensorimotor response the strength of these illusions for the IM+L group is stronger during stay in a suit than before it; for the IM group the strength of the Muller-Lyer illusion grows again after the end of the immersion. Presumably main factor influencing the strength of these illusions is the gravitational unload lowering activation level of left hemisphere that leads to use of metric representation mainly located in right hemisphere.