BACKGROUND: Determining the outcome of patients with aspergillosis can be particularly difficult because patients with aspergillosis are at risk for other conditions that mimic this infection. Galactomannan is an Aspergillus-specific antigen released during invasive aspergillosis and is detected by the quantitative serum galactomannan index (GMI) test. METHODS: Using a kappa correlation coefficient test (KCC), the strength of correlation was determined between GMI and survival outcome of aspergillosis among 56 adults with hematologic cancer (90% had myeloma) who underwent serial GMI monitoring until hospital discharge or death. RESULTS: All 56 patients received antineoplastic therapy (myeloablative followed by stem cell transplantation [autologous in 21 patients and allogeneic in 3 patients] or nonmyeloablative therapy [32 patients]). The overall correlation between survival outcome and GMI was excellent (KCC = 0.8609; 95% confidence interval [95% CI], 0.7093-1.000 [P < .0001]) and was comparable among neutropenic and nonneutropenic patients (KCC = 0.8271; 95% CI, 0.6407-1.000 [P < .0001] and KCC = 1.0; 95% CI, 1-1 [P = .0083], respectively). CONCLUSIONS: The survival outcome of patients with aspergillosis strongly correlated with serum GMI. These findings have important implications for patient care and clinical trials of mold-active antifungal agents.