The primary purpose of this study was to evaluate whether preservation of lung function parallels preservation of anatomy following elective bronchial sleeve-lobectomy (BSL). Between January 1984 and July 1988, 21 male patients (median age 51 years) with non-small cell lung cancer (n = 18), atypical carcinoid (n = 2) and inflammatory stenosis (n = 1) entered the study. Pulmonary function tests were performed pre- and postoperatively (at 3 and 12 months) and included spirometry, a quantitative perfusion lung scan and arterial blood gas analysis. The majority of operations were performed on the right lung (n = 15, 71%), with no operative deaths or major complications. Three months after surgery, the values of PaO2, PaCO2 and overall perfusion improved significantly (P less than 0.05), while there was a non significant improvement of the forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1). The only parameter correlating (r = 0.46) and significantly (p = 0.032) predicting outcome after resection was overall perfusion. The preserved, reimplanted lobe rather than contralateral lobe(s) significantly (p = 0.014) contributed to remaining overall function. In 16 patients examined 12 months post-operatively a further improvement in pulmonary function occurred. The data presented demonstrate that preservation of pulmonary function parallels preservation of anatomy following BSL and that the functional contribution of reimplanted, ipsilateral lobe(s) is of paramount importance.