In the group of 35 welders with pneumoconiosis, the evolution of radiological changes was observed, after cessation of work in exposure. In 9 cases radiological changes retreated completely; in 16 cases they were clearly reduced, whereas in the remaining 10 persons no changes in radiological picture were found. The findings indicate that the radiological changes in welders' lungs may be reversible and as such they are most probably induced by dust retention.