Rats and mice were given amiodarone by mouth at doses of 50 mg/kg/day. The drug induced accumulations of lipids within lysosomes, leading to the formation of cytoplasmic bodies. These were found in many tissues, both nervous and nonnervous, but were excluded from regions with blood-brain or blood-nerve barriers. Of nervous system regions lying outside a vascular barrier, autonomic ganglia were the most affected, with large accumulations of lysosomal bodies in nerve cells and processes, and evidence of degenerative changes. The myenteric plexus was also involved. No significant changes were seen in peripheral nerves. A limited period of increased permeability caused by nerve crush, or due to immaturity of the blood-nerve barrier resulted in the short-lived appearance of drug-induced inclusions. The rate of regeneration of axons following nerve crush was not affected, although there were small defects in myelination.