The autoradiographic method with [L-35S]methionine was used to determine the effects of a 2 h acute immobilization stress followed by a 4 h recovery on local rates of protein synthesis in the adult rat brain. Methionine incorporation into proteins was significantly increased (from 17 to 86%) in 37 out of the 39 analyzed brain structures. These results show that the stress-induced activation of the overall rate of brain protein synthesis may persist for at least 4 h after cessation of the stimulus even though the stress-related physiological variables have returned to basal levels. They suggest that increased protein synthesis may play a key role in the molecular events which lead to the neuronal plastic changes following an acute stress.