Unilateral renal artery stenosis was produced in 60 rats. Hypertension developed in 46, and was allowed to persist for various lengths of time. Nine unoperated rats served as normal controls. The adrenergic innervation pattern of the kidneys was examined by the histochemical fluorescence method. In the stenosed kidney of the early hypertensive rat there was a reduction and disappearance of the nerve pattern, particularly at the juxtaglomerular level. Prolongation of the hypertension first led to normalization of the nerve pattern in the stenosed kidney, and later to the appearance of large numbers of intensely fluorescent nerve fibres in this kidney. The possibility that the innervation alterations are the result of a denervation of the stenosed kidney followed by a re‐innervation is discussed, but found less probable. It is alternatively suggested that the findings reflect a depletion of the adrenergic transmitter due to an angiotensin‐induced increase in the release of the substance during the developmental phase of the hypertension. The findings in the stenosed kidney of late hypertensive rats may either reflect an over‐loading by adrenergic transmitter or be a non‐specific feature secondary to the contraction of the kidney par