A review of the rapidly increasing literature. The conclusions included: (a) Mammals irradiated pre- or neonatally show relatively permanent deficits in several behavioral domains, such as learning, motor functions, mating, etc. (b) Some investigators report that even small doses affect neural functions and consequently CR acquisition while other find no effects even with large doses. (c) Radiation, however, may be an UCS in avoidance conditioning. Also, several motivational variables are affected. (d) Except for vision where the results are equivocal the data on sensory functions are scant. (e) There is little evidence for long-term human changes. (f) It is emphasized that radiation may be a potentially useful tool in several areas. (195 ref.)