The axonal transport of dopamine-beta-hydroxylase (DBH; E.C. 1.14.17.1) was studied in the splanchnic nerve of the cod in vivo, and the subcellular localization of the same enzyme was studied in the chromaffin tissue from the cod head kidney. The mean rate of axonal transport for cod DBH was 18.6 mm/24 h at 10 degrees C. The mobile fraction was estimated to 22%, giving an absolute rate of transport of 85 mm/24 h at 10 degrees C. Evidence for a retrograde transport of DBH was also obtained, with an accumulation distal to a ligature of 12% of the accumulation proximal to the ligature at 3 days. DBH from the chromaffin tissue appeared to be strongly bound to the adrenergic granules, with only a small amount (ca 4%) recovered in the soluble phase.