At our institution, children diagnosed with hematologic malignancies routinely undergo general anesthesia for bone marrow aspiration/biopsy (BM) and diagnostic/ therapeutic lumbar punctures (LP). Post intervention site pain may be associated with a post dural puncture or atypical headache. Recently there have been reports of elevated Cox-2 expression in patients with CML and lymphomas. Data suggests that the combination of Cox-2 inhibitors with standard chemotherapeutics may enhance the potential of treatment for some hematological malignancies. Access to blood and cerebral spinal fluid provide a unique opportunity to determine celecoxib concentrations in the respective compartments.