The effects of noradrenaline (NA), L-3, 4-dihydroxyphenylalanine (L-DOPA), 5-hydroxydopamine (5-OHDA), 6-hydroxydopamine (6-OHDA), and reserpine (RES) on the uptake, accumulation, and release of amines in catecholamine-containing specific endothelial granules (SEG) of carp cerebral veins and their mode of formation were examined by fluorescence histochemistry and electron microscopy. The intramuscular injection of NA (4 mg/kg) or L-DOPA (200 mg/kg) resulted in an increase in both the fluorescence and electron density of SEG. After the administration of false neurotransmitters. 5-OHDA (190 mg/kg) or 6-OHDA (200 mg/kg), the venous endothelial fluorescence almost completely disappeared but the SEG electron density increased. Following the injection of RES (15 mg/kg), the fluorescence intensity and SEG electron density showed no sign of decrease, as was expected, but in fact increased. It is suggested that the SEG are able to take up and accumulate exogeneous amines and that these mechanisms are RES-resistant. The electron density of SEG increased in proportion to the amount of amines in the SEG. The swelling and fragmentation of rough endoplasmic reticulum cisternae and the accumulation of dense material within the cisternae suggests the possible participation of these organelles in SEG formation.