To describe clinical outcome with first line immunosuppression therapy for obstructive airways disease (OAD) after allogeneic BMT, we have retrospectively examined 20 long-term survivors affected by OAD. All patients had normal pulmonary function test (PFTs) before BMT. OAD was defined as FEV1 less than 80%, FER less than 80%, maximum midexpiratory flow rate of 50% vital capacity (MMFR) less than 65%, or residual volume greater than 120. Prednisone (n = 4), CsA (n = 8) and azathioprine (n = 8) have been used as first-line immunosuppression agents. Mean follow-up was 65 months (range 15-142). We identified three categories of patients according to response to treatment: complete (n = 6, 30%), partial (n = 6, 30%) or no response (n = 8, 40%). Age, FEV1, time of onset after BMT, Karnofsky index or immunosuppression modality do not seem to be related to subsequent response. However, patients with low values of MMFR and high values of RV at the beginning of therapy are likely to show poor response. In the complete response group, normalisation of PFTs is achieved within the first months of treatment (median 6 months ranging from 3 to 9 months), suggesting that prolonged therapy is not advantageous and could increase morbidity and mortality if there are no other signs of CGVHD.