To assess the value of computed tomography (CT) scanning for the diagnosis of complicated pneumoconiosis, or progressive massive fibrosis (PMF), we conducted a prospective study of 127 subjects who had worked in coal mines for at least 15 years. Sixty-two suffered simple pneumoconiosis (nodular profusion > or = 1/1 under the ILO-80 international classification system) visible on simple chest films. None were diagnosed of PMF on the basis of X-ray evidence. CT led to a diagnosis of PMF in 8 cases (6.3%; CI 95%, 2.68-11.82). PMF was category A in all 8; all of them had had chest film evidence of simple pneumoconiosis. Six (75% of these patients had q and/or r nodulation; in 5 (62.5%) the nodules tended to confluence. These figures were significantly higher (p < 0.05, Fisher's test) than in the group of patients with no PMF, among whom 54 (45.3%) had SP, 2 (1.68%) had q and or r nodulation and 3 (2.52%) tended to confluence. We observed no differences in FVC, FEV1, the FEV1/FVC ratio or DLCO between the PMF and non PMF groups. Our results suggest that CT scans can be useful for diagnosing PMF in some cases in which it is suspected bases on chest X-ray findings (simple pneumoconiosis, q and/or r nodulation, tendency to confluence).