The HLA system is extremely polymorphic. In current practice, the determination of the HLA typing of an individual is essential in the context of organ transplantation. It is also indicated in the search for susceptibility to certain pathologies, mostly autoimmune diseases. The objectives of this work, which is intended for health professionals and researchers in the field of molecular biology, are the determination of the allelic frequencies of HLA class I and II genes in a control population of 150 blood donors from the North-East of Algeria, and the realization of a case-control study with 24 patients with Multiple Sclerosis " S.E.P".