The selection of suitable reference genes is crucial for accurate quantification of gene expres-sion and can add to our understanding of host–pathogen interactions. To identify suitablereference genes in Pandora neoaphidis, an obligate aphid pathogenic fungus, the expressionof three traditional candidate genes including 18S rRNA(18S), 28S rRNA(28S) and elongationfactor 1 alpha-like protein (EF1), were measured by quantitative polymerase chain reac-tion at different developmental stages (conidia, conidia with germ tubes, short hyphae andelongated hyphae), and under different nutritional conditions. We calculated the expressionstability of candidate reference genes using four algorithms including geNorm, NormFinder,BestKeeper and Delta Ct. The analysis results revealed that the comprehensive ranking ofcandidate reference genes from the most stable to the least stable was 18S (1.189), 28S (1.414)and EF1 (3). The 18S was, therefore, the most suitable reference gene for real-time RT-PCRanalysis of gene expression under all conditions. These results will support further studieson gene expression in P. neoaphidis