Determine the utility of a polymerase chain reaction using primers for candida species performed on serum collected serially from patients undergoing bone marrow transplantation. Determine if PCR is more sensitive than blood culture in detecting invasive infection; rapid indication of infection and earlier diagnosis; how PCR results change with treatment and resolution of infection; and if in the setting of particularly high risk patients, prospective sampling affords any benefit over sampling at the time of suspicion of candida.