Substantial among-study heterogeneities were observed, while calculating risk estimate for the association between PARP1 Val762Ala polymorphism and overall cancer risk (homozygous model: P<0.001, I2 = 50.4%; heterozygous model: P<0.001, I2 = 56.2%; recessive model: P = 0.002, I2 = 43.9%; dominant model: P<0.001, I2 = 63.0% and allele comparing: P<0.001, I2 = 68.4%). The gene discussed is PARP1; the disease is cancer.