Objective To investigate the possible pathogenic mechanisms of narrow pharynx in obstructive sleep apnea syndrome (OSAS) induced by neurogenic inflammation Methods The levels of nitric oxide (NO) and calcitonin gene related peptide (CGRP) in fasting plasma and pharyngeal soft tissue homogenate from mild, moderate, and severe OSAS patients, the normal controls, and patients undergoing uvulopalatopharyngoplasty (UPPP) were detected by immunoradioassay and enzyme reduction Results Plasma NO level in serious OSAS patients was the lowest in the five groups and that in the control group was the highest [severe OSAS=(53 33?7 83) mmol/L, controls=(74 30?6 40) mmol/L, UPPP group=(68 12?7 46) mmol/L, moderate OSAS=(60 45?7 51) mmol/L, mild OSAS=(69 24?6 32) mmol/L, P 0 05) [severe OSAS =(44 18?5 80) mmol/L, moderate OSAS=(48 04?6 66), mild OSAS=(50 72?5 33) mmol/L, controls =(54 37?4 43) mmol/L, UPPP group =(54 10?3 70) mmol/L] NO level in pharyngeal tissue of OSAS increased significantly [OSAS =(0 748?0 053) ?mol/g, controls=(0 382?0 031) ?mol/g, P