The space radiation environment consists of geomagnetically trapped protons and electrons, galactic cosmic radiation, and at times, high-energy solar particles that can penetrate spacecraft and spacesuits to produce a significant radiation exposure to crewmembers. The International Space Station (ISS) era will find astronauts spending months at a time on orbit, will occur during the rise and peak of the current solar cycle, and the construction of the ISS will require astronauts to perform these tasks in thinly shielded spacesuits. In order to determine the astronaut radiation exposures and related health risks, computerized anatomical male and female models have been developed and are used in conjunction with models of the space radiation environment and spacecraft and spacesuit shielding models. The National Council on Radiation Protection and Measurements (NCRP) has identified several critical body organs that are at risk. In addition, NASA has implemented for the Space Shuttle program astronaut dose limits based on recommendations of the NCRP that are age- and gender-dependent. However, these dose limits are currently being reviewed for use on ISS and may even be lowered.In this paper, a review of the space radiation environment, spacecraft, and computerized anatomical models is discussed in detail. Results of a parametric study of body organ exposures from the trapped proton environment as a function of ISS module location, orbital altitude, and solar cycle conditions are presented. Future work will include the contribution from the galactic cosmic radiation environment to provide an estimate of the total exposure to the human body organs.