A fundamental goal of space medicine is to maintain the health and fitness of spacecrews. Meeting this goal requires reliable, effective, up-to-date medical support systems for use in microgravity. This article describes some of the factors considered in the design and assembly of Russian and U.S. in-flight medical care systems. The successful mutual use of U.S. and Russian medications and medical equipment under the NASA-Mir program conclusively demonstrated the importance and advantages of cooperation among participating space agencies. Continued progress toward the integration of U.S. and Russian flight medical systems will further increase the effectiveness of the medical support of joint missions aboard the International Space Station.