In order to accomplish a model for immunossupression in experimental conditions two lots of 50 young mice were divided into groups of 10, and submitted to dexamethasone ingestion. Two experiments were considered in the study. In the first experiment conditions for immunossupression were established in 50 mice, by per os supply of several concentrations of dexamethasone in the water given for normal daily intake ad libitum. Criteria of immunossupression considered include: hair standing on end; leukopenia by decrease of lymphocyte population; spleen atrophy in relation to controls, with severe hypoplasy of all lymphoid structures. In the second experiment another lot of 50 mice in similar conditions established for the first experiment and concerning the immunossupression were submitted to intraperitonial innoculation of near 10e Cryptococcus neoformans. Culture suspensions of cryptococci isolated from cerebrospinal fluid samples of human neurocryptococcosis cases were used for this purpose. Although fungi could be recognized in lungs, liver and spleen from every mice innoculated, only those with central nervous system involvement (near by an half of all) died. The discussion includes considerations about the role of the blood-brain barrier function in the findings registered.