Male Sprague-Dawley rats (200-300 g) were sacrificed by cervical dislocation and left either at room temperature (21-23 degrees C) for periods of 1, 2, and 4 hours or in the refrigerator (4-5 degrees C) for periods of 1, 2, 4, 8, 16, and 24 hours. The brains were left in the intact animals in order to stimulate human autopsy materials. At the end of each period, the rat was decapitated and the brain removed and immediately dissected into the following regions: cerebral cortex, striatum, midbrain, pons and medulla, and cerebellum. The levels of norepinephrine (NE) and dopamine (DA) in brain regions were determined fluorometrically. In animals kept at room temperature the level of NE decreased gradually with time reaching 61%, 76%, 68%, and 68% of control in the cerebral cortex, midbrain, pons and medulla, and cerebellum at 4 hours post mortem respectively. Striatal DA reached 61% of control at 2 hours and remained the same at 4 hours post mortem. The NE level declined at a slower rate in brain regions obtained from refrigerated animals, reaching 65%, 81%, 77%, and 77% of control in cerebral cortex, midbrain, pons and medulla, and cerebellum at 24 hours post mortem. Striatal DA reached 54% of control at 16 hours and showed no further decline at 54 hours post mortem. There was a significant post mortem decrease in NE and DA levels in all brain regions examined, however, the rate of this decline varied from region to region. The tissues obtained from refrigerated animals showed statistically less of a decline in amine levels.