The timely diagnosis of invasive aspergillosis (IA) remains difficult. In recent years, increased experience has been gained with the Platelia™ Aspergillus enzyme immunoassay. However, the excellent sensitivity and high positive predictive value that has been reported in earlier studies cannot consistently be reproduced in some of the more recent studies. As expected, this stems from major methodological and clinical heterogeneities between studies. This article reviews these between-study heterogeneities and concludes that the detection of serum galactomannan can be used to define a case of IA in a well-defined population of at-risk patients.