The effect of suramin, a strong inhibitor of lysosomal enzymes, was studied in rat superior cervical (SCG) and dorsal root ganglia (DRG). Ten days after administration both types of ganglion showed increased intraneuronal pigment fluorescence; in DRG there were also accumulated pigments in Schwann cells. Ultrastructurally the pigment bodies were membranous or lamellar inclusion bodies. In SCG suramin-induced inclusion bodies were associated with decreased catecholamine fluorescence and tyrosine hydroxylase immunoreactivity, suggesting that altered activity of lysosomal enzymes and the formation of lysosomal inclusion bodies may be coupled with decreased synthesis of neurotransmitters in rat sympathetic neurons.