To explore the expression of heme oxygenase-1 (HO-1) in the peripheral blood mononuclear cells (PBMCs) and its relationship with pulmonary ventilation function in asthmatic patients, 18 asthmatic patients and 18 healthy subjects were selected. HO-1 protein and mRNA levels in PBMCs were measured by immunohistochemical staining and reverse transcription-polymerase chain reaction (RT-PCR), respectively. Blood carbon monoxide Hb (COHb), serum total IgE and pulmonary ventilatory function were observed. Our results showed that the percentage of cells positive for immunohistochemical staining of HO-1 were significantly higher in asthmatic patients (41.72±7.44) % than that in with healthy subjects (10.45±4.36) % (P