Mutations or deletions of mitochondrial DNA (mtDNA) are associated with diabetes mellitus. In this study, we investigated the relationships between the mtDNA content in peripheral blood and surrogate indices of insulin resistance in 18 healthy young women (mean age 20.8 +/- 1.5 years). The mtDNA content was significantly correlated with the area under the curve of insulin during an oral glucose tolerance test (r = -0.622), the homeostasis model assessment for insulin resistance (r = -0.616), the ratio of fasting glucose to insulin concentration (r = 0.586) and the fasting insulin level (r = -0.552). Further study is warranted to elucidate the mechanism by which the mtDNA content is associated with insulin resistance.