Maximal expiratory flow-volume curves (MEFVC) were recorded in 610 workers using two different breathing manoeuvres. Inspiration in one was forced and maximal, while in the other, it was slow and maximal. In both manoeuvres, the ventilatory function was defined according to the diagnostic classification proposed by I. Kirin. Two groups of workers with mild obstructive changes were found. In one group, we diagnosed a condition defined as transitional state to obstructive ventilatory disorder (Tr.OVD) using both manoeuvres. In the second group, we detected normal lung functions using one of the breathing manoeuvres while the other manoeuvre disclosed Tr.OVD. In the second group, the relative share of workers scoring below the lower limits on the test of Tiffeneau was significantly lower than in the first group. Instantaneous flows also were significantly lower in the second group. Also, the FEV1, FEV1/FVC and MEF25-75% were significantly higher in the second group. The results showed that obstructions were milder in the second group than in the first. A new approach is suggested to detect obstructions milder than Tr.OVD. This approach would be practical for use in mass epidemiological screening studies because its performance does not require complicated equipment.