<p><b>OBJECTIVE</b>To explore the potential role of neuropeptide Y (NPY) in the pathophysiological process of hypertension caused by obstructive sleep apnea syndrome (OSAS).</p><p><b>METHODS</b>The concentration of serum NPY were measured with radioimmunoassay (RIA) in 417 subjects (97 normotensive controls without OSAS, 113 cases of normotensive with OSAS, 73 cases of hypertensive without OSAS and 134 cases of hypertensive with OSAS. Further, the mean NPY level were compared in four groups and the possible effective factors on NPY were discussed.</p><p><b>RESULTS</b>(1) The concentration of NPY in four groups were (50.5 +/- 37.2) pmol/L in normal controls, (76.0 +/- 39.9) pmol/L in normotensive with OSAS group, (66.9 +/- 36.2) pmol/L in hypertensive without OSAS group and (86.8 +/- 36.8) pmol/L in hypertensive with OSAS group. Whether the patients with OSAS combined with hypertension or not, the concentration of NPY in the serum raised remarkably compared with those without OSAS and hypertension, the highest level of serum NPY was detected in OSAS combined with hypertension group. (2) Pearson correlation analysis indicated that both SBP and DBP related to the serum NPY significantly in non-OSAS group (AHI <10), while the BMI, abdominal circumference, AHI as well as the lowest level of SaO2 correlated to NPY besides SBP in OSAS group with (AHI > or =10). (3) Multiple linear regression model showed that the abdominal circumference and AHI were contributing factors to SBP, while neck circumference and BMI were contributing factors to DBP. The level of NPY in the serum were significantly affected by AHI and BMI, in which the former one had greater influence.</p><p><b>CONCLUSION</b>The increased level of serum NPY may play weakly potential roles in the pathophysiological process of hypertension caused by OSAS.</p>