The effects of heparin microdoses on vagal tone (the Bayevsky heart rate variability index) and blood coagulation time were examined in 15 healthy men and women and in 14 patients with acute facial neuropathy. Nasal inhalation of heparin solution vapour (thrice every 30 sec, interrupted by a 60-80 sec interval) without changes in olfactory sensation or nasal secretion prolongs the onset and completion of blood clotting and decreased heart rate (vagal activation) in normotony volunteers. The similar procedure of distilled water nasal inhalation appears to be ineffective.