We have studied cytokine expression by the human bladder carcinoma cell line 5637 using a cDNA-PCR procedure. Transcripts for interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-6, IL-7, IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), G-CSF, M-CSF, tumor-necrosis factor-alpha (TNF-alpha), and TNF-beta were constitutively present, whereas IL-3, IL-4, IL-5, and IL-9 mRNA sequences could not be detected. This expression pattern was not altered after 12-O-tetradecanoyl-phorbol-13-acetate (TPA) stimulation (4 and 8 h) of 5637 cells. Relative expression levels of cytokines were assessed by limiting dilution of the cDNA pool. This procedure proved to be a semiquantitative technique when compared to Northern blot analysis.