Nimbolide treatment inhibited the proliferation of both bladder cancer cell lines with an IC50 value of 3 μM. Treatment of cells with nimbolide induced G2/M phase cell cycle arrest via both Chk2-Cdc25C-Cdc2/cyclin B1-Wee1 pathway and Chk2-p21WAF1-Cdc2/cyclin B1-Wee1 pathway. This evidence concerns the gene CHEK2 and urinary bladder cancer.