Our experiments with rats dealt with finding a possible functional splenic elimination by using an i.v. injection of ethyl and methyl palmitate emulsion. Simultaneously, immunological effects were determined in both substances. After applying ethyl palmitate an extensive splenic necrosis could be induced resulting in an elimination of the sequestrational splenic function to an extent comparable to surgical splenectomy. Histological examinations of liver, lungs, kidneys, heart, bone marrow, lymph nodes and thymus together with the follow-up of some metabolic indicators in the spleen and liver (determination of proteins, DNA, RNA, EFA, transaminases in blood serum and observations of proteosynthesis) showed that the effect of ethyl palmitate on the spleen is selective and that there is no marked damage of other organs. Methyl palmitate is important for its inhibition of antibody response manifesting itself in a reduced production of heteroagglutinins and in a prolonged survival time of skin semiallografts.