Objective: To determine the role of bone marrow biopsy (BMBX), performed in association with comprehensive blood and imaging tests, in the evaluation of patients with fever of unknown origin (FUO). Patients and Methods: We reviewed the medical records of 475 hospitalized patients who underwent BMBX in our medical center from January 1, 2005, to April 30, 2010. We identified 75 patients who fulfilled the accepted classic Petersdorf criteria for FUO. All patients underwent in-hospital investigation for fever, including chest and abdominal computed tomography. Results: In 20 patients (26.7%), BMBX established the final diagnosis. Sixteen patients had hematologic disorders, including 8 patients with non-Hodgkin lymphoma, 2 with acute leukemia, 1 with multiple myeloma, 1 with myelodysplastic syndrome, and 4 with myeloproliferative disorders. The remaining patients with diagnostic BMBX specimens had solid tumors (2 patients), granulomatous disease (1 patient), and hemophagocytic syndrome (1 patient). Multivariate analysis revealed the following as the significant positive predictive parameters for a diagnostic BMBX specimen: male sex (odds ratio [OR], 7.35; 95% confidence interval [CI], 1.19-45.45), clinical lymphadenopathy (OR, 21.98; 95% CI, 1.97-245.66), anemia (OR, 2.21; 95% CI, 1.28-3.80), and increased lactate dehydrogenase levels (OR, 1.003; 95% CI, 1.001-1.006). Conclusion: Bone marrow biopsy is still a useful ancillary procedure for establishing the diagnosis of FUO, particularly if used in the appropriate clinical setting. Clinical and laboratory parameters associated with hematologic disease are predictive of a diagnostic BMBX specimen in patients with FUO.