['Asthma is a common condition in general medical practice, and it accounts for about 1% of all ambulatory hospital visits. Nowadays, hospitalization rates for asthma have actually been increased in some demographic subgroups despite recent advances in treatment. Understanding the underlying factors that contribute to hospitalization and especially duration of the hospitalization of asthmatics could help elucidate the recent rise in morbidity and also reduce the high demand on health care systems of the disease. The aim of this study was to evaluate factors affecting the duration of hospitalization for Iranian patients with asthma.', "This study was conducted on 55 asthmatic patients (diagnosis of asthma was in accordance with the criteria of the American Thoracic Society). The study was performed on patients hospitalized in Rasoul-e-Akram hospital in Tehran, Iran during the period 2005-2006. During hospitalization, the patients' most common complaints were recorded as the symptoms and signs of the medical condition, results of physical examinations, spirometry, arterial blood gas analysis (ABG), and ICU admission.", "There were 18(32.7%) male and 37(67.3%) female patients with a mean age of 54.96 (SD=17.54) years. The mean duration of hospitalization was 8.31(SD=4.69) days that ranged between 2 and 23 days. The mean baseline arterial PH (p=0.039, RPearso = -0.362), baseline arterial [HCO3] (p=0.042, RPearson = 0.361), changes of FEV1 after bronchodilator (p=0.041, RPearson= -0.363) and patient's age (p=0.002, RPearson=0.0433) were determined as factors affecting duration of hospitalization."] Do arterial blood gas and spirometry parameters affect the length of stay in hospitalized asthmatic patients?