From 1978 to 1988, 148 bilobectomies (21 upper and middle and 127 lower and middle) were performed for bronchogenic carcinoma. A conservative procedure was mandatory in 29 patients in whom a pneumonectomy was not functionally feasible while bilobectomy was deliberately performed in 119 patients with near normal lung function. Overall mortality was 6% compared to 4% and 3%, respectively, following pneumonectomies and lobectomies. Preoperative functional status did not significantly influence mortality. The complication rate was 55%. The incidence of bronchopleural fistula electively observed after lower and middle lobe resection was significantly higher (11%) compared to 4% after pneumonectomy and 1.4% after lobectomy (P less than 0.01). The overall 5-year survival was 43% and was similar to that observed at comparable TNM stage after other pulmonary resections. Residual right pulmonary function demonstrated by perfusion isotopic scan was 24% +/- 10 in 21 long-term survivors. These results indicate that bilobectomy can reasonably be considered in patients requiring more than a lobectomy but in whom lung conservation is mandatory despite a significant increase in morbidity. The risk appears justifiable regarding late survival results and functional benefit of the remaining right lobe.