The matrix metalloproteinase-2 gene (MMP2) was found to be associated with hip structure in pigs. Recently three quantitative trait loci (QTLs) for loin muscle area were found on chromosome 6, to which MMP2 was mapped. In the present study, association analyses were conducted in two pig populations for a single-nucleotide polymorphism (SNP) c.-1959C>G present at a putative promoter region of the MMP2 gene. The association results showed that the animals with the C allele have a significantly larger loin muscle area than that of the animals with the G allele (P < 0.05). To confirm the present results, further functional studies and an additional causative SNP discovery in pigs with various genetic backgrounds are necessary.