Background: The rapidity of progression of amyotrophic lateral sclerosis (ALS) to death or respiratory failure impacts patients, clinicians, and clinical investigators. The aim of this study is to evaluate of the pulmonary function tests (PFTs) in patients with ALS and the association between these PFTs and survival Methods: A total of 36 ALS patients who PFTs, including vital capacity (VC), maximum mid-expiratory flow rate (MMEFR), forced vital capacity (FVC), and forced expiratory volume in 1 s (FEV1), were available from the time of diagnosis were included in this study. Nonpulmonary characteristics assessed at the time of PFTs. Data were analyzed using chi-square, Student’s independent t-test, Kaplan-Meier, correlation, and receiver operating characteristic (ROC) curve.Results: The mean age of subjects was 55.36 (SD = 12.24) year, and the male to female ratio was 2.6. Twenty-Cve (69.4%) were died in 5 years period of our study. The mean and median survival time (In months) was calculated as 42.51 (95% co Cdence interval [CI] 33.64- 51.39) and 38 (95% CI 27.23-48.77) months, respectively. The rate of ALS survival was 74% at 1st year, 41% at 3rd year and 10% at 5th year of starting symptoms. The results of Kaplan-Meier test showed survival was significantly longer in the group with PFTs closer to normal. In addition, ROC analysis showed that FVC < 50% could potentially be a predictor of death in ALS patients (P = 0.003, area under curve = 0.649). Conclusion: We found single measures of upright FVC, FEV1 to be significantly associated with survival, even after controlling for relevant non-pulmonary patient characteristics. Our study demonstrated that upright FVC, FEV1, VC, and MMEFR are useful non-invasive measures in the prediction of survival in ALS.