Recent work on the transport of high-energy massive particles (protons, neutrons, alpha particles, etc.) through dense matter as it applies to the shielding of manned space vehicles is reviewed. The transport of heavy particles through tissue and the resultant physical dose (rad) is considered, but the important question of the biological effects of radiation is not discussed. Throughout the discussion an attempt is made to indicate the areas of uncertainty where further research is required and particularly to indicate the areas where experimental confirmation of theoretical results is needed.