There are closed relations between progressive systemic sclerosis (PSS) and exposure to quartz dust in the GDR. The recognition of PSS as an occupational disease is regulated by law. By analysis of the dust exposed working places a limit for silica concentrations were fixed. It is unlikely, that silica concentrations below 10% in the respirable dust induce a PSS. There are no significant differences in lung function of PSS-patients with and without quartz exposure.