A multi-discipline, multi-year collaborative spaceflight research program (NASA/Mir Science Program) has been established between the United States and Russia utilizing the capabilities of the Russian Mir Space Station and the NASA space shuttle fleet. As a key research discipline to be carried out onboard Mir, fundamental biology research encompasses three basic objectives: first, to investigate long-term effects of microgravity upon plant and avian physiology and developmental biology; second, to investigate the long-term effects of microgravity upon circadian rhythm patterns of biological systems; and third, to characterize the long-term radiation environment (internal and external) of the Russian Mir space station.The first joint U.S./Russian fundamental biology research on-board Mir is scheduled to begin in March, 1995 with the Mir mission 18 and conclude with the docking of the U.S. shuttle to Mir in June, 1995 during the STS-71, Spacelab/Mir Mission-1 (SLM-1). The two collaborative experiments originally included on the Mir-18 mission, lncubator-2 and Greenhouse-2, have added a new dimension to the technical and scientific cooperation between the two countries. In addition, the extended, 90-day (and greater for subsequent Mir mission segments), on-orbit duration of the mission is a feature that provides new opportunities and challenges. The first docking of the Shuttle to the Mir station also introduces some significant experiment design issues: launching hardware, science payloads, and U.S. crew on Russian vehicles and returning a similar complement to Earth via the Shuttle and/or Spacelab/Spacehab have many implications for the teams of scientists and engineers involved in the endeavor. First, scientific interests, goals, and objectives must be made compatible. Second, hardware and science requirements must be suited to the environment of the Mir space station. Finally, and perhaps most importantly, the substantial differences in the approaches each country takes in the design and development of scientific experiments and supporting equipment must be understood and accommodated to ensure a successful scientific partnership. The effort required to learn to work together successfully is expected to have long-term benefits: the joint U.S./Russian program will provide the U.S. science community, as well as NASA engineers and managers, with the hands-on experience needed to support future International Space Station development efforts.This paper provides a brief overview of the scientific goals and objectives and of the supporting equipment for conducting the fundamental biology research program onboard the Mir space station. Important issues involved in developing the payloads that can operate successfully onboard the Mir are addressed as well as key benefits from the U.S. / Russian collaborations.