The objective of this study was to analyse the epidemiologic, clinical, radiological and functional characteristics as well as the evolutive pattern of a group of patients diagnosed of round atelectasis (RA). Patients with a radiological diagnosis of RA were retrospectively identified from January 1993 to January 1998. Cases with diagnosis not confirmed by high resolution computerized axial tomography (HRCAT) were excluded. A total of 29 patients were identified, with a mean age of 65 +/- 13 years (27 men and 2 women). At diagnosis 14 patients (34%) were smokers and 14 (49%) ex-smokers. Regarding occupation, 11 individuals (38%) had history of occupational exposure to asbestos. Regarding symptomatology, round atelectasis was a radiological finding in 15 patients (52%) and the most common symptom was chest pain (34%). The most common findings detected in the chest X-ray included pleural thickening (45%), pleural effusion (38%), nodular lesion (34%) and loss of volume (24%). The most common changes detected by HRCAT were pleural thickening (45%) and bronchovascular arch (55%). In two cases magnetic resonance (MR) was performed and in no case did this examination provided additional information for the diagnosis of RA. Functional respiratory examination did not identify and predominant pattern. During the follow-up period (2.2 years) 24 patients (83%) remained radiologically stabilized, one improved and the other four worsened (two due to enlargement and two due to increase in number). Chest X-ray is a good method for the presumptive diagnosis of RA. HRCAT is an excellent technique to confirm the diagnosis and rule out the presence of malignancy. MR provides no additional information in the study of RA. There is a frequent association between RA and asbestos exposure.