Orbiting spacecraft provide a valuable laboratory for experiments on physical and biological systems in a reduced gravity environment. In these experiments, fluid masses containing bubbles and drops are encountered routinely. This original work provides a clear, thorough review of the motion of bubbles and drops in reduced gravity, particularly motion caused by variations in interfacial tension arising from temperature gradients on their surfaces. The emphasis is on theoretical analysis from first principles; experimental results are discussed and compared with predictions where appropriate. Students and researchers interested in fluid mechanics in reduced gravity will welcome this state-of-the-art reference.