Objectives: To find a correlation between Lung function with the disease activity in Rheumatoid arthritis. Methods: The study was carried out on 40 (35 female and 5 male) patients with active RA who fulfilled the ARA 1987 reversed criteria for the classification of RA. Patients with signs and symptoms of respiratory disease or chest injury were excluded from this study. The patients were all examine clinically by weighted and selective index of active of synovitis and assessed for functional status of the follwing; ESR, Hb % level pulmonary function tests including FEV1, VC, FEV,/ FVC and DLCO. Another group of 30 (27 female and 3 male) patients with active RA served as a control group. Results: The results showed that Hb level ranged between (7- 13.3 gm/dl), ESR ranged between 11-131 mm/hr and restrictive ventilatory defect was observed in 15 (37.5%) patients. Obstructive ventilator defect was presened in 10 (25%) patients. And decrease DLCO was detected in 23 (51.5%) patients. There was a positive correlation between PETS with Hb%, ESR, Disease duration and activity of synovitis (p< 0.05). Conclusion: The Lung function can be used to stratify abnormalities in a clinically useful manner and can be used as an indicator of disease activity in RA.