SUMMARYTwelve patients with cavitating lung lesions of uncertain aetiology, who had percutaneous aspiration combined with the instillation of radiographic contrast media, are presented. A diagnosis was made in 11 of the 12 patients (92%). A positive culture was obtained in all patients already receiving treatment for lung abscesses. Cultures of lavage fluid were positive in 89% of infected cavities. The instillation of radiographic contrast media into the lung cavity assists biopsy of the cavity wall, can be used to lavage the cavity, and may facilitate expectoration of sputum.