Nasal discharge have many small amount of proteins. These proteins are composed of albumin, immunoglobulin, lysozyme, protease and protease inhibitor. Alpha 1-antitrypsin is classified as protease inhibitor. It has been reported that during acute inflammation of human upper respiratory tract, the activity of trypsin inhibitor is decreased in nasal discharge. Hochstrasser, et al., reported that, varying amount of alpha 1-antitrypsin existed as a non-active, protein-bound form during respiratory infections, and the proportion of this masked inhibitor to the total inhibitor was an indicator for judging the severity of the inflammatory process. During acute inflammation, the activity of these proteases and protease inhibitor increase in the local site. This study was performed to find out variation of alpha 1-antitrypsin in nasal discharge and serum among various upper resoiratory tract diseases. The author collected 53 nasal discharge from acute rhinitis (12 cases) acute sinusitis (12 cases) chronic rhinitis (12 cases) chronic sinusitis (12 cases) and maxillary cyst (5 cases). Nasal discharge were more liquified by small amount of 0.2M EDTA. Quantity of nasal discharge and cystic fluid were measured by Radial-immunodiffusion method. At the same time, author measured alpha 1-antitrypsin in serum simultaneously and searched for correlations between nasal discharge, cystic fluid and serum. The following results were obtained 1) Amount of AAT of nasal discharge in chronic sinusitis (38.78±14.62mg/dl) was higher than that in acute sinusitis (15.82±3.30mg/dl). 2) Amount of AAT of mucopurulent discharge (23.90±14.90mg/dl was higher than that of watery discharge (9.25±1.92mg/dl). 3) In sinusitis, amount of AAT of nasal discharge in severe group (27.80±13.15mg/dl) was higher than that in mild group (19.92±3.50mg/dl). 4) Amount of AAT of nasal discharge in infectious group (22.56±15.49mg/dl) was higher than that in allergic group (11.96±4.21mg/dl). 5) Therefore, in rhinitis and sinusitis, amount of AAT in systemic section like serum is normal range but that in local section like nasal discharge was affected by duration, severity and cause of inflammation.