The concentration of IL-33 in the pleural effusion of the patients with TPE (22.96±0.98 ng/l) was significantly higher than that in the patients with MPE (12.60±5.15 ng/l; P<0.01); however, the concentration of serum IL-33 in the patients with TPE was not significantly different to that in the patients with MPE (P>0.05). This evidence concerns the gene IL33 and Pleural effusion.