Cytokine biosynthesis is tightly regulated by a number of processes, including gene expression control. Posttranscriptional control of cytokine gene expression offers a fine-tuning mechanism that contributes not only to transient biosynthesis of cytokines, but also helps in rapid and early initiation of the cytokine response. Deregulation of cytokine biosynthesis has been associated with a number of disease conditions, including autoimmune diseases, cancer, and others. Thus, there is a need for accurate measurement of posttranscriptional gene expression events in cytokine research. The method described here is a cell-based GFP assay that quantitatively measures posttranscriptional effects. This method is used for assessing the effects of modulators and conditions that lead to changes in posttranscriptional gene expression during cytokine production or for assessment of cytokine action on posttranscriptional events of gene expression.