The aim of our study was to investigate the activity of sympathetic nerves in arteries as a possible factor in the development of hypertension. In this paper, we report our results on the uptake of norepinephrine by the arteries of spontaneously hypertensive rats (SHR). Tail arteries of 7--9 week-old SHR and of normotensive controls (WKY) were incubated with [3H]norepinephrine for various periods of time. The 3H content in vessels of SHR and WKY was identical after 5 min but significantly higher in SHR after 15, 30, 60 and 90 min incubation. The rate of time-related uptake was greater in SHR as revealed by analysis of variance. The uptake of [3H]norepinephrine after 60 min was substantially less in vessels treated with cocaine in inhibit neuronal uptake or with desoxycorticosterone to inhibit extraneuronal uptake. After MAO activity was blocked with pargyline. 3H content remained higher in arteries of SHR than in those of WKY but after catechol-O-methyltransferase (COMT) was inhibited by U-0521, the difference was not significant. Our results demonstrate an alteration in the function of the sympathetic nerves in arteries as indicated by enhanced uptake of norepinephrine in the tail arteries of young SHR prior to the full development of hypertension.