AbstractWe describe a simplified and sensitive polymerase chain reaction (PCR)‐based method for the quantification of low‐abundance RNA for mouse cytokine receptor genes. Accurate quantification is achieved in a two‐step protocol which uses a synthetic RNA as an internal standard. The proper titration of the amount of mRNA molecules is followed by a kinetic analysis which ensures precise measurement. This quantitative PCR method provides a rapid and reliable way to quantify the amount of cytokine receptor mRNA in samples containing as few as 1000 molecules of RNA for a cytokine receptor target gene. We illustrate our approach by quantifying mRNA levels for two families of cytokine receptor genes in the fetal liver and bone marrow of the mouse. Our results reveal early and abundant expression of the genes encoding the signal transducing subunits interleukin‐2 receptor γ and gp130. Their expression seems to precede that of the genes encoding the specific subunits of these interleukin receptor systems.