Surgical removal of the spleen is a well established procedure which is indicated for various hematologic disorders. Patients who are poor surgical risks may be considered for nonsurgical 'splenectomy' using an embolization technique. This new technique should only be performed in patients who represent high surgical risk. The possible effectiveness of this procedure should be previously tested with the use of intraarterial vasopressin infusion. The following conditions should be fulfilled: (1) small emboli should be used to eliminate collateral flow; (2) the procedure should be carried out in two or three stages to minimize flank pain and the risk of massive splenic necrosis; and (3) most important, the spleen should be surgically removed as soon as the hematologic condition has improved in order to prevent splenic abscess formation. Splenic embolization was carried out in three patients with hypersplenism. One survived but was helped by the procedure. Two died, one definitely and the other possibly as a result of the embolization. These discouraging results were reproduced in the animal laboratory where 11 of 14 animals developed severe complications, six of which were acutely fatal. The high incidence of late complications precludes nonsurgical splenectomy as a routine procedure, but it can be carried out provided the spleen can be removed surgically.