The relation between the development of hypertension and changes in behavior was investigated. Hypertension was induced by unilateral application of a 0.20-mm clip around the renal artery. At 4 weeks, but not at 1 week, after the operation an increase in ambulation was found. Blood pressure was significantly increased at 1 (28 mm Hg) and 4 weeks (78 mm Hg) after the operation. In a second experiment, renal hypertensive rats and controls were either regularly handled (i.e., subjected to indirect tail-cuff blood pressure measurements) or left undisturbed. At 4 weeks after clip implantation, only in the nonhandled rats with renal hypertension, an increase in open-field ambulation was found. Blood pressure was markedly increased in both handled and nonhandled renal hypertensive rats.