The integrated processes of nuclear industry are considered to define the nature of wastes. Processes for recovery and preparation of U and Th fuels produce wastes containing concentrated radioactive materials which present problems of confinement and dispersal. Fundamentals of waste treatment are considered from the standpoint of processes in which radioactive materials become a factor such as naturally occurring feed materials, fission products, and elements produced by parasitic neutron capture. In addition, the origin of concentrated fission product wastes is examined, as well as characteristics of present wastes and the level of fission products in wastes. Also, comments are included on high-level wastes from processes other than solvent extraction, active gaseous wastes, and low- to intermediate-level liquid wastes. (J.R.D.)