We investigated patients with obstructive variants (FEV1/VC less than 65%) of FSS (N = 9) and IPF (N = 12) and assessed the course of the lung function parameters of AO during observation times of 2 to 10 years. Three groups of patients could be formed: group 1 (N = 9), no significant change of FEV1/VC and Raw; group 2 (N = 3), significant decrease of FEV1/VC and significant increase of Raw; group 3 (N = 7), divergent changes of FEV1/VC and Raw. Two patients died before they could be assigned to a group. The definite constancy of FEV1/VC (group 1 and the majority of group 3) assessed in this long-term study corroborated our previous results. Thus the great majority of our patients showed no deterioration of AO. "Divergency" of Raw (group 3) can at least partially be interpreted as "false positive." The prognosis of the obstructive variants is essentially not inferior to that of the nonobstructive groups in these two conditions.