Longer on-orbit crew stay times anticipated during the construction and habitation of the International Space Station (ISS) will necessarily require the development of a new generation of radiation measurement instrumentation. The planned orbit of 51.6° inclination at 470 km will result in significantly higher daily crew exposures than experienced during the bulk of previous U.S. space missions. In addition, the National Commission for Radiation Protection and Measurement (NCRP) is revising the guidelines for crew radiation exposures. It is anticipated that the new guidelines will call for dose and dose-equivalent limits that are substantially less than those currently used in the space program. The cornerstone elements of the planned radiation measurement instrumentation for the ISS are a tissue-equivalent proportional counter (TEPC) and a directional charged particle spectrometer. These active systems will be supported by NASA's standard passive (thermoluminescent) dosimetry system. The concepts, designs, development, and evaluation of the active measurement systems are discussed, and individual system application is examined. Typical results of active system prototypes flown on the Space Shuttle and the Mir station are presented and discussed.