Background: A serum galactomannan (GM) assay has been approved for diagnosing invasive aspergillosis (IA). However, the role of the BAL-GM assay has not been well established. Therefore, we conducted a metaanalysis to determine the overall accuracy of BAL-GM in the diagnosis of IA. Methods: After a systematic review of English-language studies, the sensitivity (SEN), specificity (SPE), and positive and negative likelihood ratios (PLR and NLR, respectively) of BAL-GM for the diagnosis of IA were pooled using a bivariate metaanalysis. Hierarchic summary receiver operating characteristic curves were used to summarize overall test performance. Potential between-study heterogeneity was explored by subgroup analyses. We calculated posttest probability to evaluate clinical usefulness. Results: Twelve reports, including 13 studies, met our inclusion criteria. The summary estimates of the BAL-GM assay for proven or probable IA were as follows: SEN, 0.90 (95% CI, 0.79-0.96); SPE, 0.94 (95% CI, 0.90-0.96); PLR, 14.87 (95% CI, 8.89-24.90); and NLR, 0.10 (95% CI, 0.04-0.24). The four summary estimates of the BAL-GM assay for proven IA were 0.94 (95% CI, 0.86-0.98), 0.79 (95% CI, 0.68-0.86), 4.41 (95% CI, 2.87-6.77), and 0.07 (95% CI, 0.03-0.09), respectively. Significant heterogeneity was present. Conclusions: BAL-GM determination is a sensitive and specific test for the diagnosis of proven and probable IA. The measurement of BAL-GM is thus likely to be a useful tool for diagnosing IA. Further studies focused on the impact of treatment agents are needed. © 2010 American College of Chest Physicians.