Matrix metalloproteinase-2 (MMP-2) is a well-known mediator of cancer metastasis but is also thought to be involved in several aspects of cancer development, including cell growth and inflammation. We comprehensively characterized genetic variation across the MMP-2 gene and evaluated associations with breast cancer risk using a two-phase (phase 1 and phase 2) study design. A total of 39 polymorphisms were genotyped among 6,066 Chinese women participating in the Shanghai Breast Cancer Study, a population-based case-control study. Two MMP-2 promoter polymorphisms were found to have consistent results between phase 1 and phase 2 participants, and to be significantly associated with breast cancer risk among all genotyped participants. Minor allele homozygotes for rs11644561 (G/A) were found to have a decreased risk of breast cancer [odds ratio (OR), 0.6; 95% confidence interval (CI), 0.3-1.0] compared with major allele homozygotes, as were minor allele homozygotes for rs11643630 (T/G) compared with major allele homozygotes (OR, 0.8; 95% CI, 0.7-1.0). When analyzed together, a rare haplotype (4.4%) with both rs11644561 A and rs11643630 G was found to have a significantly reduced risk of breast cancer (OR, 0.6; 95% CI, 0.4-0.8). In addition, rare allele homozygotes for rs243865 (-1306 C/T) tended to have an increased risk of breast cancer (OR, 1.4; 95% CI, 0.9-2.4). Together, these findings support a role for MMP-2 genetic variation in breast cancer susceptibility.