The aim of the study was to evaluate urinary albumin excretion (UAE) in cancer patients with neutropenic fever and to correlate UAE with the acute-phase response and secretion of proinflammatory cytokines. UAE and serum values of C-reactive protein (CRP), interleukin-6 (IL-6), and tumour necrosis factor-alpha (TNF-alpha) were measured in 32 consecutive cancer patients during episodes of neutropenic fever. UAE increased during fever reaching a peak level 36 h after the onset of fever. CRP, IL-6 and TNF-alpha had peak levels within the first 24 h. UAE correlated significantly with CRP, IL-6 and TNF-alpha. UAE was higher in patients with microbiologically documented infections than in patients with unexplained fever at the time of fever development, whereas UAE was similar in patients with either microbiologically or clinically documented infections. The results suggest a glomerular leakage of albumin secondary to an activated inflammatory response in neutropenic patients with fever. UAE may be a simple and sensitive test in monitoring the acute response to infection in the neutropenic patient.