We have studied the influence of steric factors on the clinico-pathologic expression of immune complex-mediated glomerular diseases, utilizing ferritin as an exogenous antigen. The tracer was planted in the left kidney either in the subepithelial layer of the glomerular capillary wall or on the endothelium and lamina rara interna. Subepithelial immune complex formation resulted in non-inflammatory injury with heterologous and autologous proteinuric phases (115 +/- 16 mg/24 hrs on day 2; 183 +/- 16 mg/24 hrs on day 9) lasting four to five weeks. The glomerular filtration rate of the experimental left kidney was reduced by 19% at day 3, and was increased by 20% at day 12 over right kidney values. Immune complexes persisted for more than seven weeks in the lamina rara externa. In contrast, immune complex deposition on the endothelium and in the lamina rara interna led to acute transient anuria, with a 38% drop in glomerular filtration rate at one hour, massive platelet accumulation, followed by a strong inflammatory response. Proteinuria did not develop. Functional and structural integrity was restored within 24 hours, with complete clearing of immune deposits. We conclude that the distribution of exogenous antigens within the capillary wall determines the structural and functional expression of immune-mediated glomerular diseases.