Many reference genes are used by different laboratories for gene expression analyses to indicate the relative amount of inputRNA/DNA in the experiment. These reference genes are supposed to show least variation among the treatments and withthe control sets in a given experiment. However, expression of reference genes varies significantly from one set ofexperiment to the other. Thus, selection of reference genes depends on the experimental conditions. Sometimes the averageexpression of two or three reference genes is taken as standard. This review consolidated the details of about 120 genesattempted for normalization during comparative expression analysis in 16 different plants. Plant species included in thisreview are Arabidopsis thaliana, cotton (Gossypium hirsutum), tobacco (Nicotiana benthamiana and N. tabacum), soybean(Glycine max), rice (Oryza sativa), blueberry (Vaccinium corymbosum), tomato (Solanum lycopersicum), wheat (Triticumaestivum), potato (Solanum tuberosum), sugar cane (Saccharum sp.), carrot (Daucus carota), coffee (Coffea arabica),cucumber (Cucumis sativus), kiwi (Actinidia deliciosa) and grape (Vitis vinifera). The list includes model and cultivatedcrop plants from both monocot and dicot classes. We have categorized plant-wise the reference genes that have been usedfor expression analyses in any or all of the four different conditions such as biotic stress, abiotic stress, developmentalstages and various organs and tissues, reported till date. This review serves as a guide during the reference gene hunt forgene expression analysis studies.