BACKGROUND--Accurate diagnosis of peripheral pulmonary lesions usually relies on fluoroscopic guided procedures. As fluoroscopy is not routinely available in many respiratory units, an approach not using fluoroscopy but with a high diagnostic yield is highly desirable. METHODS--Immediate cytological examination of multiple brushings using Riu's stain, a modified Wright's stain, was performed in 38 patients with peripheral pulmonary lesions not visible at bronchoscopy. The results were compared with the final diagnoses determined by histological examination or subsequent Papanicolaou staining of cytological specimens and clinical course. RESULTS--Of the 38 patients 29 were subsequently confirmed to have a malignant tumour. Our method provided a diagnosis of malignancy in 86% of these lesions. The accuracy (91%) and sensitivity (88%) were higher for lesions > 3 cm in diameter than for those of diameter < or = 3 cm (87% and 83%). There were no false positive results. The 29 lesions correctly diagnosed as malignant by Riu's stain required significantly fewer brushings (mean (SD) 3 (2)) than the nine benign lesions (5 (4)). CONCLUSIONS--This technique provides a high diagnostic yield, avoids the need for fluoroscopy, and is probably safer than percutaneous biopsy.