Growth of head and neck squamous cell carcinoma (HNSCC) is generally associated with an inflammatory component. It is hypothesized that these tumor cells develop mechanisms to evade the growth inhibitory effects of cytokines that are present in the tumor microenvironment. This study determined the changes in responsiveness to inflammatory cytokines that accompany the transition of normal to transformed epithelial cells. Paired primary cultures of normal epithelial cells (NEC) and SCC cells were established from 16 patients. Receptor-mediated activation of signal transducer and activator of transcription and extracellular signal-regulated kinase pathways in response to cytokine treatments was identified by immunoblot analysis. Thymidine incorporation determined the impact of the cytokines on DNA synthesis. HNNEC and HNSCC displayed a prominent signaling in response to oncostatin M, interleukin-6, IFN-gamma, and epidermal growth factor. Untreated HNSCC showed an elevated level of phosphorylated signal transducer and activator of transcription 3 and extracellular signal-regulated kinase (P < 0.001) compared with HNNEC, suggesting constitutively activated pathways. Moreover, HNSCC cells phosphorylated significantly more signal transducer and activator of transcription 1 in response to oncostatin M (P = 0.002) and IFN-gamma (P = 0.018) treatments. DNA synthesis of SCC cells was less inhibited by cytokines produced by endotoxin-stimulated macrophages (P = 0.016) than that of NEC. Low-dose oncostatin M slightly enhanced proliferation of SCC, whereas that of NEC was suppressed (P = 0.016). This study identified significant alterations in signal transduction pathways engaged by cytokines and which are associated with loss of growth inhibition of HNSCC. Increased signal transducer and activator of transcription phosphorylation, along with constitutively phosphorylated extracellular signal-regulated kinase in HNSCC, suggest that these pathways as molecular markers are important in the malignant transformation process and are potential targets for treatment.