The combination of isobutylmethylxanthine, insulin and dexamethasone (MIX treatment) is widely used to differentiate 3T3-L1 fibroblasts to mature adipocytes. In the preliminary experiment performed to determine the role of glucocorticoid receptor, a single treatment with RU486, a glucocorticoid receptor antagonist, was counterintuitively found to be sufficient to induce adipogenesis with smaller lipid droplets than MIX treatment. Here we aimed to characterize the RU486-induced adipocytes by DNA microarray analysis and compare to those in the adipose tissues. Total RNAs isolated from the undifferentiated 3T3-L1 fibroblasts (control cells) and the adipocytes induced by 5-day treatment with 1 micromolar RU486 (RU cells) and those induced by MIX treatment (MIX cells) were subjected to analysis with an Affimetrix Clariom S Mouse DNA chip. The microarray data of the mouse epididymal and inguinal adipose tissues were obtained from GEO DataSet in NCBI, the National Institute of Health, USA. Transcriptome Analysis Console 4.0.2 (Thermo Fischer Scientific) was use to analyze the data. The primary component analysis revealed that the RU cells were closer to epididymal and inguinal adipose tissues in terms of primary component 2 and 3, respectively, than MIX cells or control cells. Forty four genes were found to be common between RU cells and epididymal adipose tissues. The findings indicate RU486 induces adipocytes closer to those of in vivo adipose tissues than MIX treatment. Single treatment with RU486 is suggested to be a novel method to induce normal adipogenesis.