Complicated pulmonary unilocular cystic hydatidosis (CPUCH) is a serious condition, which requires immediate treatment. The aim of the present study was to evaluate the efficacy of fibreoptic bronchoscopy (FOB) in the final diagnosis of CPUCH. Of 1,726 cases, who underwent FOB evaluation between 1990 and 1994 in our centre, 24 patients (17 females and 7 males), who had proven CPUCH after thoracotomy, were included in this study. Fourteen of the 24 cases were diagnosed in the preoperative period by cytological and histopathological evaluation of FOB material, whereas the remaining 10 cases with presumed CPUCH underwent thoracotomy for final diagnosis. Of the 14 cases diagnosed by FOB (11 females and 3 males); none had concomitant extrapulmonary hydatid disease. Whitish-yellow membranes were seen in 12 of the cases during FOB. Whilst cuticular particles, degenerated scoleces, and hooklets were seen in 14 cases in bronchial lavage, these elements were identified in brushing material in only seven. In 10 of the 14 cases, cytological diagnosis was confirmed by FOB biopsies before thoracotomy. It is concluded that whilst the clinical, radiological and laboratory findings are presumptive, fibreoptic bronchoscopic examination and the cytological and histopathological examination of material obtained during that procedure are conclusive for the diagnosis of complicated pulmonary unilocular cystic hydatidosis.