As rhinostereometry, an optical measurement method, allows meticulous studies of changes in nasal mucosa congestion, the mucosal reaction in eight healthy volunteers was studied with this technique before, during and after 20 minutes' chilling of the feet in cold water. In five volunteers there were no observable mucosal reactions. In three volunteers the mucosal congestion changed but not uniformly, and not in such a way that the change could be explained as an effect of chilling of the feet. In four volunteers there was a clearly observable increased nasal secretion. This gives a possible explanation of the increased nasal breathing resistance observed in similar studies using rhinomanometry as the measuring method.