Objective:Differentiating asthma from chronic obstructive pulmonary disease (COPD) is difficult. Steroid trial may be of help but has several pitfalls. The present study aims to assess the value of past clinical profile of asthma and its differential diagnosis from COPD in male smokers and thereby to formulate clinical parameters to diagnose bronchial asthma in such patients.Patients and Methods:Male smokers who reported at the Respiratory Medicine Department of the National Institute of Medical Sciences (NIMS) Hospital, Jaipur, (India), with shortness of breath (SOB) and showing less than 12% postbronchodilator bronchial reversibility (BR) on spirometry were recruited. These patients were given oral prednisolone 1 mg/kg for two weeks. Post steroid (PS) spirometry was performed to ascertain BR. The past clinical history was recorded and analyzed to determine if it is of any use in differentiating asthma from COPD.Result:Out of 104 patients, four were lost to follow up, 52 were diagnosed as bronchial asthma, and the remaining 48 as COPD. It was revealed that past history of (H/O) seasonal variation, wheezing, eye allergy, nasal allergy, dust allergy, skin allergy, and family H/O asthma/allergy were positive in 50, 40, 34, 30, 18, 14, and 12 asthma patients as compared to 10, 8, 2, 4, 6, 0, and 0 in 48 COPD patients (P < 0.001). The odds ratio (OR) for diagnosing asthma was highest for the presence of any other two symptoms/variables, besides SOB, in the past (OR = 275, P < 0.0001).Conclusion:Past clinical history is of immense value in differentiating asthma from COPD in male smokers presenting with SOB and fixed airway obstruction.