To assess the autonomic control of the microcirculation in human skin and nasal mucosa, the spontaneous fluctuations of a laser Doppler signal recorded on forearm skin and nasal mucosa were compared with heart rate fluctuations and the respiratory signal in 11 healthy subjects by means of spectral analysis. Possible direct mechanical-thermal effects of airflow on the nasal mucosa were evaluated by comparing recordings obtained when the subjects were breathing through either the nose or the mouth. Comparison of the spectral analysis of the signal obtained for skin and nasal mucosa blood flow allowed us to define the characteristics of the autonomic tone of the microcirculation in these two areas. The skin is mainly influenced by sympathetic activity, and the nasal blood flow is regulated by both sympathetic and parasympathetic activity.