Housekeeping genes are commonly used as internal standards in quantitative RNA studies to normalize expression levels. However, their expression can vary under different experimental conditions, limiting their reliability. This study examines the use and limitations of housekeeping genes such as β-actin, glyceraldehyde-3-phosphate dehydrogenase (G3PDH), and L32 as internal standards in various experimental models. The study shows that while these genes are often considered stable, their expression can change in response to factors like cell type, culture conditions, and experimental treatments. For example, in studies involving nerve and immune cells, G3PDH and 18S rRNA were found to be relatively stable, making them suitable internal standards. However, in other contexts, such as in vitro cultures with mitogens, variations in L32 and G3PDH expression were observed, suggesting that rRNA (18S and 28S) may be more reliable in such cases. The study recommends using multiple housekeeping genes or rRNA as internal standards to ensure accuracy, especially when variations are expected. It also emphasizes the importance of careful experimental design, including proper RNA quality control, statistical methods, and data interpretation. Overall, while housekeeping genes are widely used, their suitability as internal standards depends on the specific experimental conditions and cell types involved.Housekeeping genes are commonly used as internal standards in quantitative RNA studies to normalize expression levels. However, their expression can vary under different experimental conditions, limiting their reliability. This study examines the use and limitations of housekeeping genes such as β-actin, glyceraldehyde-3-phosphate dehydrogenase (G3PDH), and L32 as internal standards in various experimental models. The study shows that while these genes are often considered stable, their expression can change in response to factors like cell type, culture conditions, and experimental treatments. For example, in studies involving nerve and immune cells, G3PDH and 18S rRNA were found to be relatively stable, making them suitable internal standards. However, in other contexts, such as in vitro cultures with mitogens, variations in L32 and G3PDH expression were observed, suggesting that rRNA (18S and 28S) may be more reliable in such cases. The study recommends using multiple housekeeping genes or rRNA as internal standards to ensure accuracy, especially when variations are expected. It also emphasizes the importance of careful experimental design, including proper RNA quality control, statistical methods, and data interpretation. Overall, while housekeeping genes are widely used, their suitability as internal standards depends on the specific experimental conditions and cell types involved.