Forty-two children receiving bone marrow autografts were studied prospectively regarding acute pulmonary complications; there was no procedure-related mortality and only one case of interstitial pneumonitis. An analysis was also made of the pulmonary function tests (PFTs) of the 27 autografted children who were disease-free and had been followed up for at least 1 year (median 4.1 years, range 1.1-7.6 years). PFTs were performed before and 6, 12, 24, 36 and 60 months after autologous BMT. The mean pre-transplant values of total lung capacity (TLC), vital capacity (VC) and forced expiratory volume in one second (FEV1) were close to predicted but 6 months after autologous BMT there was a statistically significant decrease (11, 13 and 15% below baseline, respectively) in patients receiving total body irradiation in their conditioning regimen. There was some but not complete recovery with time. DLCO remained low throughout the study, irrespective of the conditioning regimen. In summary, acute pulmonary complications were few and PFTs showed only modest changes from baseline after ABMT. At the latest follow-up no respiratory symptoms had reportedly occurred in any of the children and the chest radiographs were normal. Although the results are promising so far, long-term follow-up is necessary to evaluate the final outcome in these children.