The analysis of 30 years of Russian EVA experience and research on earth enables us to make a number of fundamental conclusions (1, 2, 3, 4, 5, 6 and 7). The suit life support subsystem (LSS) parameters including gas composition, gas pressure, thermal control system, provide for environments close to those of physiological norm. The Russian EVA suit allows a crewmember to retain necessary scope of motions, tactile sensibility, and the ability to see and communicate which are necessary for performing scientific and repair activities outside the spacecraft. The duration of space missions (up to a year) and repetition of EVAs every 2-3 days do not affect crewmember capability to perform the EVA tasks with the metabolic rate of 320 kcal/h during the 6-7 hour EVA sortie. Medical monitoring and analysis of the LSS parameters allow us to reliably control crewmember state of health, forecast and prevent its unfavourable changes. The analysis of aviation, diving and space medicine experience states that possibility of DCS during the EVA is comparatively low.