Objective: Cell division cycle 42 (CDC42) participates in the pathogenesis of some T-cell-mediated inflammatory diseases via regulating CD4 + T-cell differentiation and inflammation response. This study aimed to evaluate the correlation of CDC42 and T helper (Th)1/Th2 cytokines with disease risk, effusion viscosity, and hearing loss degree of otitis media with effusion (OME). Methods: CDC42, interleukin (IL)-4, and interferon-gamma (IFNγ) in effusion and serum of 78 OME patients were determined by enzyme-linked immunosorbent assay. Besides, the effusion (irrigating fluid) and serum samples of 30 controls (adenoid hypertrophy patients without OME) were also obtained for CDC42, IL-4, and IFNγ determination. How to cite this article: Wu D, Yang Y, Duan C. Cell division cycle 42 positively correlates with T helper 2 cytokine, effusion viscosity, and hearing loss degree in otitis media with effusion patients.