FOR its possibility of revascularizing an ischemicmyocardium through collaterals, production of pericardial splenosis was attempted in a series of dogs by autotransplantation of fragmented splenic tissue into the pericardial sac. Pericardial splenosis occurred in every instance and by 6 months was extensive and associated with diffuse pericardial adhesions interposed with splenotic tissue. Coronary arterial injection studies showed the splenosis to be in vascular continuity and, hence, the possibility of its functioning as a collateral supply to the coronaries. The profuse vascularity of splenic tissue, the relative simplicity of production of pericardial splenosis, and its demonstrated vascular continuity with the coronary arteries without need of epicardiectomy would appear to make pericardial splenosis a possible and practical procedure. Splenosis occurs in humans after an interval after splenectomy for ruptured spleen. The peritoneal surfaces are seeded with fragments of tissue torn from the spleen at the time of rupture and distributed by the