Soluble extracts of Cryptococcus neoformans were examined for their ability to induce a macrophageregulatory T-suppressor cell known to appear in the spleens of mice infected with cryptococci. Suppressor cells were induced by injection of extracts of encapsulated or thinly encapsulated strains of cryptococci, Dose-response analysis showed that as little as 25 ,ug of soluble capsular polysaccharide antigen could induce significant suppressor cell activity, with maximum suppression occurring at a dose of 100 ,ug. The suppressor * Corresponding author.