Osteomyelitis (OM) is a bone infection characterized by necrosis and new formation of bone. Because matrix metalloproteases (MMPs) play an important role in bone extracellular matrix remodeling, we investigated the role of some MMP polymorphisms in OM patients. A total of 118 OM patients and 300 blood donors were genotyped for the polymorphisms of MMP1 (-1607 1G/2G) and MMP13 (-77A/G). Levels of MMPs (-1, -2, -3, -8, -9, -10, and -13) and tissue inhibitors of metaloproteases (TIMP-1, -2, and -4) in serum and in human osteoblasts obtained from OM biopsies also were determined. The MMP1 (-1607 2G/2G) genotype was significantly more frequent among OM patients compared with controls [65.3% versus 33.7%, chi(2) = 26.85, odds ratio (OR) = 3.24, 95% confidence interval (CI) 2.03-5.2, p < .0001]. The MMP1 2G allele also was more frequent in OM patients (73.3% versus 57.2%, chi(2) = 37.76, OR = 2.75, 95% CI 1.96-3.85, p < .0001). Carriers of the 2G allele had significantly higher osteoblast MMP1 mRNA and MMP-1 serum levels than noncarriers (p < .04). Interleukin 1alpha (IL-1alpha) increased MMP-1 and -13 protein secretion and Ets1 mRNA expression by OM patients' osteoblasts. No association of the MMP13 (-77 A/G) polymorphism with OM was observed. The MMP1 (-1607 1G/2G) polymorphism might contribute to OM pathogenesis. This could be due to increased expression of MMP-1 by osteoblasts and is regulated by IL-1alpha.