Formaldehyde is a substance which is widely used in several work fields, including many medical and biological sectors. It appears that formaldehyde exposure may cause bronchial asthma. Little information is available, however, with regard to upper aereal tracts. The nose is a target organ of major importance for a large range of professional and extra-professional environmental pollutants. In particular, cases of professional rhinitis brought about by exposure to disinfectants have been reported in Literature. In the light of general knowledge related to the close correlation between upper and lower airways, and to the lack of information concerning the effects of short-term formaldehyde exposure on the upper aereal tract, the Authors decided that investigation of such exposure might prove interesting as well as worthwhile. A group of fifteen technicians who work in three different pathology departments and who had been exposed to formaldehyde for at least one year were studied. The purpose of the study was to assess possible alteration in nasal resistances at the end of a normal work shift. The subjects under study were observed according to a procedure which included several clinical, allergological, serological and functional evaluations carried out on specific days of the week. A control group, consisting of eight asymptomatic, non-atopic subjects who had never been exposed to inhalation of irritants was also monitored in the same way. Conclusions were drawn after considering some important variables such as exposure time, possible anatomical alterations of the nose, the presence of respiratory allergies and smoking habits. It was apparent that professional formaldehyde exposure typical of that experienced by technicians working in pathology departments induced a short-term irritant effect on the upper aereal tract, which, even though subclinical, is revealed by a statistically significant increase in nasal resistance. This effect seems to be favoured (at statistically not significant levels) by atopy, cigarette smoking and anatomical alterations of the nose. Our data seem to exclude a chronic cumulative effect of formaldehyde exposure.