Bone marrow transplantation has become a beneficial and curative technique used in treatment of patients with different hematologic conditions. It has become widely used at our institution for hematologic malignancies and certain resistant solid tumors. However, this treatment can result in immunosuppression, with an increased chance of infection. The purpose of this study was to review the causes of infections and determine the number of patients diagnosed with sinusitis. In the retrospective study, we evaluated the cases of bone marrow transplant patients for incidence and cause of fever. Sixty-eight percent of patients had fever after transplant; of these, 59% had fever of unknown origin. Only 1% of the patients with fever were diagnosed with sinusitis. In the evaluation of fever, sinusitis was not usually suspected and therefore was not included in the differential diagnosis. With such a high percentage of fever of unknown origin in this growing patient population, appropriate pretreatment evaluation of each case to rule out sinusitis should be considered.