Two types of experimental GN induced by immunological procedures. Heymann-type AIC-GN and NTN, were treated with anticoagulant agents. Dipyridamole, aspirin, ticlopidine or batroxobin was administered either to rats with AIC-GN for 14 to 28 days or to NTN rats 2 days prior to injection with NTS and 14 to 21 days thereafter. A significant decrease in the amount of urinary protein was observed only in rats treated with 12.5 to 50.0 mg/kg dipyridamole daily, whereas no significant decrease in proteinuria was observed in either AIC-GN or NTN rats treated with the other agents. Histopathologically, no improvement in the light and electron microscopic findings was noted in AIC-GN rats treated with these agents, even with dipyridamole. On the other hand, in NTN rats, light and electron microscopic study of the kidneys from rats sacrificed 30 to 60 min after NTS injection revealed that platelet aggregation and inflammatory changes in the glomeruli were remarkable reduced in rats pretreated with 56.4 mg/kg aspirin or 50.0 mg/tg triclopidine daily, but no difference in the renal lesions between rats treated with aspirin or triclopidine and control animals were observed 2 weeks after NTS injection. No histological improvement was observed in rats pretreated with dipyridamole. It would be reasonable to conclude from these results that the favorable effect of dipyridamole on proteinuria is not related to its antiplatelet activity and that platelet aggregation is not essential to the development of renal lesions in rat AIC-GN and NTN. (J Lab Clin Med 99:428, 1982.)