Background: Growth of oral squamous cell carcinoma is generally associated with an inflammatory component. It is hypothesized that tumor cellsevade the growth inhibitory effects of cytokines present in the tumor microenvironment. Oncostatin-M (OSM) is an inflammatory cytokine produced by macrophages and T lymphocytes as well as tumor cells, it inhibits the proliferation and induces differentiation of a number of types of tumors. This study aimed to study OSM expression on both gene and protein levels.Methods: In vitro study done on thirty (OSCC) cases obtained from paraffin blocks and ten normal epithelial tissues used as control. For each case immunohistochemical examination of OSM protein intissues as well as quantitative real time polymerase chain reaction(RT-PCR) were done for determination of expression of both OSM gene and its specific receptor, finally results were statistically analyzed using ANOVA test.