Objective: To compare muscle sympathetic nerve activity (MSNA) in age- and weight-matched African-Americans and American Caucasians with primary hypertension. Design: Using microneurography, we compared MSNA at rest and in response to cold-pressor testing and handgrip exercise in 13 hypertensive African-Americans and 12 hypertensive American Caucasians. Methods: All subjects were withdrawn from antihypertensive medications for at least 2 weeks before the study. MSNA was recorded from the left peroneal nerve. Results: Resting MSNA was similar in the Blacks and the Caucasians. Increases in muscle efferent activity, mean arterial pressure and heart rate in response to the cold pressure and handgrip exercise were not significantly different in Black and in Caucasian subjects. Conclusion: MSNA, either at rest or in response to certain laboratory Stressors, is not different in Black and in Caucasian hypertensive subjects with similar resting blood pressures. © Current Science Ltd.