Matrix metalloproteinases (MMPs) may contribute to the development of endometriosis. Genetic variations in several MMP promoters may influence the transcription and expression of MMPs. The purpose of the present study was to assess how gene polymorphisms in the MMP1 and MMP3 promoters affect the risk of development of endometriosis. We genotyped 100 women with endometriosis and 150 control subjects in North China. There was a significant difference in frequency of the MMP1 genotype between cases and controls (P=0.03). The 2G homozygote in endometriosis and controls was significantly different (P=0.02). The frequency of the 2G allele among affected women (79%) was significantly higher than among the healthy controls (66.9%; P=0.003). However, the overall genotype and allelotype distribution of the MMP3 single nucleotide polymorphism (SNP) in patients was not different from that of controls (P> or =0.05). MMP1 and MMP3 polymorphisms were in linkage disequilibrium in cases and controls (D'=0.47; P=0.00). The haplotype frequency distribution derived from these two polymorphisms was significantly different between cases and controls (P=0.00). The haplotype analysis suggested an implication of both MMP1 and MMP3 polymorphisms in the susceptibility to endometriosis. We conclude that the MMP1 promoter SNP and MMP 2G/6A haplotype may modify susceptibility to endometriosis, but that the MMP3 promoter SNP is unlikely to be associated with endometriosis in the population of North China.