Hypocholesterolemia, which often accompanies infectious diseases has been suggested to serve as a prognostic marker in hospitalized patients. Even though patients with chemotherapyinduced leukopenia are at high risk of infection and mortality, only limited information is available on serum cholesterol levels in these patients. We therefore measured serum cholesterol levels in 17 patients with hematological malignancies during chemotherapyinduced neutropenia and correlated it with clinical outcome. Patients with fever (>38.5 degreesC) showed a significant decrease in serum cholesterol levels within 24 hours. Eight days after onset of the fever nonsurvivors had significantly lower serum cholesterol levels (median 2.09 mmol/l, range 0.492.79, n=6) compared to survivors (median 3.23 mmol/l, range 1.684.86, n=11). Cholesterol levels in survivors returned to baseline levels at the time of discharge from the hospital. At the onset of fever, serum levels of inflammatory cytokines interleukin-6, tumor necrosis factor (TNF) and soluble TNF receptors p55 and p75 were elevated in all patients, but only TNF and TNF receptor p75 levels were significantly different in survivors and nonsurvivors. Our data suggest that a decrease in serum cholesterol levels is a prognostic marker in neutropenic patients with fever. Release of inflammatory cytokines may in part be responsible for hypocholesterolemia in these patients.