THE SUCCESS of bone marrow transplantation in the treatment of aplastic anemia and acute leukemia has resulted in an increasingly large number of long-term survivors of this procedure. The occurrence of infections in these patients has been recognized as a major cause of morbidity and mortality, particularly in those patients in whom chronic graft-v-host disease develops.<sup>1</sup><i>Streptococcus pneumoniae</i>has been noted to cause a substantial portion of the reported infections,<sup>1,2</sup>and it has been suggested that immunization with polyvalent pneumococcal vaccine and long-term antibiotic prophylaxis be used to prevent this complication.<sup>2</sup> Reports of pneumococci both resistant to penicillin in vitro and producing clinically important infection have been a cause of great concern.<sup>3</sup>While some of these organisms have been found to be resistant to sulfamethoxazole-trimethoprim as well as penicillin,<sup>3</sup>there have been, to our knowledge, no reports of penicillin-sensitive/sulfamethoxazole-trimethoprim-resistant pneumococci causing clinical infection. We report