This investigation of 68 hemodialysis patients (ages 33 to 91) analyzed the association of biochemical indicators of vitamin K nutriture and bone metabolism, and related both to past bone fracture history and prospective bone fracture risk. Phylloquinone concentrations were significantly lower in the 23 patients with previous fractures compared to those without (0.93 vs. 1.50 nmol/liter, P < 0.003) and a smaller percentage of their serum osteocalcin was carboxylated (48.8 vs. 53.6%, P < 0.03). The 41 patients who never had fractures had nearly three times higher phylloquinone concentrations than the nine patients with fractures during a four-year follow-up period (1.59 vs. 0.55 nmol/liter, P < 0.002) and more carboxylated serum osteocalcin (55.2 vs. 42.0%, P < 0.01). None of the patients with phylloquinone concentrations over 2.2 nmol/liter had elevated intact parathyroid hormone (iPTH) concentrations, and only patients with less than 1 nmol/liter phylloquinone had severe hyperparathyroidism (iPTH > 300 ng/liter). Our data thus indicate that suboptimal vitamin K nutriture in hemodialysis patients is associated both with increased bone fracture risk and with a high prevalence of hyperparathyroidism.