Six experiments (Exp.) were conducted to determine the effect of dietary K1 on selected plasma characteristics and bone ash and to determine the dietary K1 requirement for young turkeys. In Exp. 1, diets were supplemented with 0, 0.5, 1.0 or 2.0 mg of K1/kg. All diets contained 1,650 IU of vitamin D3 (D3)/kg. Dietary K1 had no effect on tibia ash at 7 d. In Exp. 2, a 2 x 4 factorial arrangement was used consisting of 1650 or 550 IU of D3/kg and 0.1, 0.45, 1.0 and 2.0 mg of K1/kg. Dietary D3 and K1 had no effect on bone ash. In Exp. 3, dietary treatments consisted of a Control (1,650 IU of D3 and 2.0 mg of K1/kg) and K1 concentrations of 0, 0.37, 2.28, or 5.33 mg/kg in diets containing 275 IU of D3/kg. Poults fed the low D3 diet without K1 consumed less feed and gained less weight, and had increased plasma alkaline phosphatase activity, decreased inorganic phosphorus level and decreased tibia ash compared with those of poults fed the Control diet. Feed intake and body weight gain were improved, plasma alkaline phosphatase activity decreased, and plasma inorganic phosphorus increased when poults were fed the low D3 diet supplemented with 0.37 or 2.88 mg of K1/kg. Tibia ash of poults fed the low D3 diet was not affected by K1 supplementation. In Exp. 4, a 2 x 3 factorial arrangement was used with 0 or 75mg of neomycin/L in the drinking water and 0, 0.1 or 0.5 mg of dietary K1/kg. PT was reduced to a nadir and PC in plasma increased to a plateau when diets contained 0.1 mg of K1/kg. Dietary K1 concentrations tested in Exp. 5 and 6 were 0, 0.08, 0.31 or 0.44 mg/kg and 0, 0.1, 0.25, 0.5 or 2.0 mg/kg, respectively. The results of Exp. 5 indicated that the dietary K1 requirement was 0.079mg, based on the influence of dietary K1 on PT. In Exp. 6, The K1 requirement was estimated to be 0.099 and 0.13 mg/kg, on the basis of PT and PC, respectively.