Vascular endothelial growth factor (VEGF) has utility in the treatment of intimal hyperplasia, hypertension and atherosclerosis, and of conditions susceptible to treatment with agents that produce nitric oxide or prostacyclin. Instead of VEGF, an equivalent agent such as an agonist of VEGF receptors may be given, as may nucleic acid encoding such an agonist. The agent may successfully be administered via the adventitial surface of a blood vessel, e.g. using a device which defines a reservoir between the body wall and the vessel's adventitial surface, the reservoir being at least part-filled bya pharmaceutical formulation containing the agent to be delivered.