A total of 105 male and 60 female patients were screened in the respiratory medicine outpatients' department, Institute of Postgraduate Medical Education & Research, Kolkata between December, 2002 and January, 2005. Chronic obstructive pulmonary disease patients were diagnosed on the basis of history and clinical examination while patients with body mass index > or =25 and otherwise disease-free were grouped as overweights. Patients suffering from other diseases like systemic hypertension, etc, were referred from other departments after proper evaluation. The patients and controls (n=10) each for male and female groups were subjected to spirometry using computerised electronic spirometer while exercise tolerance was evaluated by modified Harvard step test. Thirty-nine male and 21 female patients were diagnosed and grouped in chronic obstructive pulmonary disease group. Both purely obstructive [forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC)% pred<70 and reduced FEV1% pred] and mixed (both obstructive and restrictive pattern ie, FEV1/FVC% pred normal or supernormal, FVC% pred <80 indicating restrictive pattern and forced expiratory flow between 25% and 75% of the vital capacity (FEF(25-75)) pred or peak expiratory flow rate (PEFR)% pred <70 indicating early small airway obstruction pattern were seen in both sexes. Although the exercise tolerance values were non-significant in both sexes in chronic obstructive pulmonary disease obstructive pattern group, in mixed pattern group it was seen significant reduction compared to control. Hypertensives (21 males and 7 females) showed obstructive spirometric pattern. Exercise tolerance values were significantly reduced compared to controls. Male overweights (n=13) showed restrictive pattern while female overweights (n=8) showed obstructive pattern in spirometry. Exercise tolerance values were non-significant compared to control in both the groups. In ischaemic heart disease patients (n=6) FEV1%pred showed significant reduction in spirometry. In patients suffering from type 2 diabetes mellitus (n=4), post-tuberculous group (n=7), hypothyroid (n=6), collagen vascular disease group (n=6) showed restrictive spirometric pattern and the above groups including IHD patients showed significant reduction in exercise tolerance values. Some authors have stated that mixed ventilatory defect is characterised by low FEV1/FVC% pred in spirometry and low lung volumes where the lung volumes have to be ascertained by other methods but in the present investigation it was observed that mixed ventilatory defect can be estimated by spirometry; PEFR and/or FEF(25-75%). pred <70% whereas FEV1/FVC% pred is normal or supernormal. This finding is completely new one to predict mixed ventilatory defect.