A cross sectional analysis of the relation between exposure to an artificial aluminium silicate (alunite residue) and pulmonary function changes has been made in 32 subjects, 17 of whom had been previously reported and in whom there was suggestive evidence of a dose response relation between gas transfer and total silicate exposure. Longitudinal data were also available for nine subjects. No dose effect relation was observed in either analysis and only one of the three subjects previously observed to have an abnormal chest radiograph (the index subject) had deteriorated appreciably. Respirable particles of alunite residue were injected intratracheally into Syrian hamsters. No evidence of pulmonary toxicity was seen as judged by bronchoalveolar lavage measurements of the concentrations lactic dehydrogenase, albumin, and the lambda fraction of gold, and the numbers of macrophages, polymorphonuclear cells, and red blood cells (alpha-quartz and ferrous oxide were used as positive and negative controls). These results do not support a significant toxic effect of this aluminium silicate on the lungs.