Bone marrow evaluation is an important and effective way of diagnosing and evaluating primary hematologic and metastatic neoplasms as well as nonhematologic disorders. Many variations exist for obtaining marrow samples (sites, instruments, techniques); however, the method outlined in this article has proven reliable. Complete evaluation of bone marrow samples should include a brief patient history, pertinent laboratory data, peripheral blood films, bone marrow aspirate smears and sections, and biopsy imprints and sections. Routine examination of the bone marrow as described previously is usually adequate for interpretation. However, application of additional studies using cytochemical, immunocytochemical, immunohistochemical, cytogenetic, and molecular techniques may prove to be of critical importance in the diagnosis of hematologic malignancies.