The antinociceptive effect of vitamin K₂ (menatetrenone) in diabetic mice was examined using a tail-pressure test. Intraperitoneal injection of menatetrenone (10 - 100 mg/kg) produced a dose-dependent increase in the nociceptive threshold in diabetic mice. There was no significant difference between non-diabetic and diabetic mice in the menatetrenone-induced changes in the nociceptive threshold. The results suggest the therapeutical usefulness of menatetrenone for treating painful diabetic neuropathy and osteoporosis.