Objective To investigate association between tumor necrosis factor alpha (TNF-α)and obsessive compulsive disorder (OCD) in Chinese Han population. Methods Plasma concentrations of TNF-α were measured in 61 drug-free patients who fulfilled DSM-Ⅳ criteria for OCD and 93 healthy controls. TNF-α concentrations in blood were determined by enzyme-linked immunosorbent assay ( ELISA ).Two polymorphisms of TNF-α gene were investigated in the same patients and healthy controls: - 308 G/A and - 238 G/A. The allelic and genotypic frequencies of these polymorphisms were examined by using DNA sequencing method. Results Plasma levels of TNF-α did not differ between patients and controls ( P =0. 292 ). No significant results were observed for any of the alleles at the - 308 G/A or - 238 G/A polymorphism of the TNF-α gene. Finally a haplotype consisting of genotypes of these two markers was also examined. No association was observed for any haplotype ( P = 0. 108). Conclusion No significant differences were observed between patients and controls in plasma levels of TNF-α . There is no association between the -308 G/A and -238 G/A TNF-α gene polymorphisms and OCD in our Chinese samples.However, the results need to be replicated in larger samples.