The mouse has been suggested as a host for comparative studies of several aspects of Human Acquired Immune Deficiency Syndrome (AIDS). Models include studies where part or all of the genome of Human Immunodeficiency Virus (HIV) has been incorporated into murine DNA in living mice. However, the most promising opportunities for study of immunological changes, vaccine development, cofactor involvement in disease, and anti-retroviral and immunostimulatory drug testing involve infection with murine retroviruses which cause many functional changes similar to AIDS. The viruses' effects on immune systems are reviewed with special emphasis. LP-BM5 murine leukemia virus which infects T and B cells, and macrophages. LP-BM5 infection suppresses cell functions while causing polyclonal lymphocyte activation. Murine immunological characterization, availability of inbred mouse strains, economy of using mice versus primates or humans models, and similarity of immune change caused by murine retroviruses compared to those seen in AIDS caused by HIV encourage rapid development of the LP-BM5 murine leukemia model.