Microneurography is a valuable and safe method for direct intraneural recording of sympathetic nerve activity to muscle and skin in humans. The technique and its application for the study of autonomic function will be briefly discussed. The regulation of muscle sympathetic nerve activity will be focused in different clinical situations and or stimuli, such as: essential hypertension, mineralocorticoid induced hypertension, exercise mental arithmetic stress, cold pressor test, hyperinsulinemia, oral alcohol ingestion.