Guinea-pig inferior mesenteric ganglia (IMG)/hypogastric nerve preparations were incubated in tissue culture media containing ethylene glycol-bis-(beta-aminoethyl ether)N,N'tetra-acetic acid (EGTA) or colchicine and examined either by fluorescence microscopy or by transmission electron microscopy. Two millimolar EGTA inhibited the accumulation of noradrenaline (NA) fluophore proximal to a crush, but did not produce an increase in the fluorescent intensity of, or the number of dense-cored vesicles (DCVs) within the neuronal perikarya. Calcium ions, but not magnesium ions, were able to block this effect of EGTA. Preparations incubated in the presence of colchicine (2.5 microgram/ml) showed a reduction in the amount of fluorescent material accumulating proximal to a crush, but an increase in both the fluorescent intensity and the number of DCVs within the neuronal perikarya. The suggestion that calcium ions are required for the synthesis of some part of the NA-containing vesicle rather than for their loading onto the axoplasmic transport mechanism is discussed.