BACKGROUND : Inhalation of NO2 leads to a progressive airflow limitation and the development of emphysema-like lesions. We report on the efficacy of hydrogen sulfide (NaHS) for alleviating NO2-induced pulmonary impairment. METHODS : Sprague Dawley rats were exposed to 20 ppm NO2 for 6 h over six consecutive days for 75 days. At day 75, rats who had developed NO2-induced emphysema were then divided into sodium hydrosulfide (NaHS) administrated group, placebo (NaCl) group and spontaneous recovery group for about one month (days 76-105); Pulmonary function (PF) and hematological and biochemical indices were measured at days 14, 45, 75, and 105. RESULTS : NO2 exposure for 75 days was associated with a significant decrease in FEV100/FVC%, an increased in functional residual capacity (FRC), and histologic evidence of emphysema, moreover; NO2 exposure led to elevated triglyceride (TG), red blood cell (RBC), hemoglobin (HGB), and hematocrit (HCT) levels. Impaired rats treated with NaHS showed no further deterioration in PF compared to rats exposed to ambient air and elevated WBC, granulocyte and lymphocyte counts and HDL-C levels to rats given NaCl. CONCLUSIONS : NO2 exposure causes emphysema and a decline in PF in rats. NaHS could alleviate the PF decline as possible indicated by an elevation of HDL-C levels and leukocyte. NaHS has therapeutic potential for emphysema caused by air pollutant NO2.