The maximal expiratory flow-volume (MEFV) curve were measured in 195 healthy adults. The results indicated that the values of the peak expiratory flow rate, V_(75), V_(50) and V_(25), were all higher in males than in females, and the higher the age, the lower the end expiratory flow rate. The end expiratory flow rate in chronic obstructive pulmonary disease (COPD) was decreased as the disease deteriorated. In healthy subjects, the V_(50)/V_(35) was increased with age, while in COPD patients V_(50) was decreased. The more severe the condition, the lower the rate. The authors suggest that the measurement of MEFV be used as a simple valuable method to evaluate small air way functiovs.