In the present paper are discussed the diagnostic problems in M.S., there has been difficulty in certain diagnostic on the first modest signs in a proportion perhaps as high as 20% and the absence of a specific and reliable laboratory test has long been felt. This study describes two specific laboratory tests in M.S. The MEM-LAD test (macrophage electrophoretic mobility linoleic acid depression) and the E-UFA test (erythrocyte-unsaturated fatty acid). It may be noted that whilst the E-UFA and MEM-LAD test will diagnose (or esclude) M.S. the former is simpler, but is limited to M.S., the latter on the other hand once mastered is applicable in the whole range of clinical immunology were lymphocyte sensitisation is to be measured.