Objective Neutrophil/lymphocyte ratio (NLR) is a simple and reliable inflammation biomarker but few studies have assessed the relationship between NLR and hypertension in Chinese population. In order to evaluate how NLR is related to the incidence of hypertension, we designed a large scale prospective cohort study in an adult population. Method Participants were recruited from Tianjin Medical University's General Hospital?Health Management Centre. Hypertension?free subjects (men, 13 638;women,15 212) were followed up for a median of 2.7 years. Adjusted Cox proportional hazards regression models were used to assess relationships between the quintiles of NLR and the incidence of hypertension. Result During the follow-up period, 1 348 subjects in men and 476 subjects in women developed hypertension. The hazard ratios of hypertension incidence were evaluated in increasing NLR quintiles both in men and women. In the final multivariate models, the hazard ratios (95% confidence interval) for hypertension across NLR quintiles were 1.00 (Reference), 1.05 (0.87, 1.26), 1.02 (0.85, 1.22), 1.07 (0.90, 1.29) and 1.22 (1.03, 1.45) (P for trend=0.01), in men;1.00 (Reference), 1.11 (0.82, 1.49), 0.79 (0.58, 1.08), 1.13 (0.85, 1.52) and 1.25 (0.94, 1.66) (P for trend=0.07), in women, respectively. Conclusion This study showed that the elevated NLR levels were significantly related to an increased risk of developing hypertension in men, but not in women.