If you are unsure of the correct housekeeping gene(s), review the literature and technical information in your field to determine which gene(s) other researchers commonly use. It is recommended that multiple housekeeping genes be utilized for each gene expression experiment, to account for any impact that an experimental condition may have on the expression of an individual housekeeping gene. For a systematic assessment of which housekeeping genes are appropriate for your specific experimental conditions, we recommend using the Housekeeping Genes RT2 Profiler PCR Arrays for human (330231 PAHS-000), mouse (330231 PAMM-000), or rat (330231 PARN-000). These arrays consist of 8 sets of 12 common housekeeping genes. They are a valuable tool for easily identifying genes with a constant level of expression among your different experimental conditions.