The Mercury and Gemini space flights have provided approximately 2,000 manhours of weightless exposure which can be used in comparing flight results with the predicted effects of manned space flight. In general the environmental hazards and the effects upon man appear to be of less magnitude than originally anticipated. The effects noted on the various body systems are summarized. The principal physiologic changes noted were orthostatism for some 50 hours post-flight, reduced red cell mass, and reduced X-ray density in the os calcis and the small finger. Much was learned about man's ability to work in a pressurized suit in the extravehicular condition. Early biochemical findings have pointed the way to future investigations. All of these findings are of importance in relation to the planning for future long duration missions. Although much remains to be learned, it does appear from an overview of this medical legacy that if man is properly supported and evaluated his limitations will not be a barrier to the exploration of the universe.