Moderate heterogeneities were found for the studies assessing the association between NQO1 Pro187Ser polymorphism and bladder cancer risk (homozygous model: P = 0.009, I2 = 52.8%; heterozygous model: P = 0.034, I2 = 44.1%; recessive model: P = 0.015, I2 = 49.8%; dominant model: P = 0.016, I2 = 49.4%, and allele comparing: P = 0.008, I2 = 53.3%). The gene discussed is NQO1; the disease is urinary bladder cancer.