1. The sympathetic innervation of the cod coeliac artery has been investigated. An isolated nerve-artery in vitro preparation, including the coeliac artery, the splanchnic nerve and parts of the sympathetic chains was used. 2. Preganglionic fibres of the pathways producing contraction of the coeliac artery after nerve stimulation seem to leave the central nervous system via the rami communicantes from spinal nerves 1 (and/or 2)-6. The main outflow seems to be via the rami communicantes of the spinal nerve 3. 3. The contraction of the coeliac artery produced by electrical stimulation of the splanchnic nerve, was unaffected by the cholinergic blocking agent atropine (10 −6−10 −5 M), but could be abolished with the alpha adrenergic blocking agent phentolamine (10 −6−10 −5 M), which indicates an effect of stimulation via alpha adrenoceptors. 4. A weak relaxation appeared at each electrical stimulation after blockade of the contraction. The relaxation was probably mediated via beta adrenoceptors, since it was blocked by the beta adrenergic blocking agents propranolol (10 −6 M) or sotalol (10 −6 M), but was unaffected by atropine (10 −6−10 −5 M). 5. No indications of a functioning cholinergic postganglionic innervation was obtained. 6. The response to electrical stimulation of the inflow to the coeliac ganglion could, in contrast to the response to stimulation of the splanchnic nerve, be blocked by the ganglionic blocking agents hexamethonium (10 −5−10 −4 M) or mecamylamine (10 −6−10 −5 M). It is concluded that the cell bodies of the postganglionic neurones to the coeliac artery are mainly located in the coeliac ganglion. 7. Fluorescent histochemistry showed a concentration of the adrenergic innervation in the border between the adventitia and the media of the coeliac artery; no fibres appeared to enter the media.