Systemic sclerosis is frequently complicated by fibrosing alveolitis although clinical and radiological abnormalities are not usually apparent until the lung disease is well established. The aim of this study was to investigate pulmonary involvement in systemic sclerosis by thin section CT scan, bronchoalveolar lavage (BAL) and 99mTc-DTPA clearance studies, and assess the value of these tests in defining pulmonary abnormalities in patients with a normal chest radiograph. Patients were divided into those with an abnormal chest radiograph (Group I, n = 14) and those with a normal chest radiograph (Group II, n = 16). CT scans were abnormal in all patients in Group I and 7 of 16 (44%) in Group II. BAL inflammatory cell counts were raised in all 12 (100%) patients studied in Group I and 11 of 15 (73%) in Group II. There was no difference in the type of inflammatory cells observed between the two groups. 99mTc-DTPA clearance was faster than normal controls in ten of 14 patients (71%) in Group I and seven of 15 (47%) in Group II and correlated with carbon monoxide transfer factor (P less than 0.05). Lung biopsies were performed on nine patients in Group I and three in Group II all of whom had abnormal CT scans. Fibrosing alveolitis was confirmed in every case. Group II biopsies could not be distinguished from Group I biopsies; both showed fibrosis as well as inflammation suggesting that pulmonary fibrosis is an early abnormality in systemic sclerosis. Our results indicate that CT scans, BAL and 99mTc-DTPA are frequently abnormal in asymptomatic patients with systemic sclerosis who have normal chest radiographs. When the CT scan is normal abnormalities of BAL and/or 99mTc-DTPA (99mTechnetium diethylenetriamine pentacetate) clearance may indicate lung disease at a still earlier stage. This observation requires further investigation.