The denitrfication rates (DR) of sediment in Saginaw Bay, Lake Huron, have been measured with No production method. Triplicate samples of sediment core were collected at two GLERL long-term monitoring sites of the Bay in July and August of 1995. The DR is 16. 0-39,6 and 22. 7-26. 1 micromol N:/(m²·h) in the Inner and Outer regions of Saginaw Bay. respectively. The spatial and temporal characters of DR in Saginaw Bay was studied also in this paper, The DR was influenced by the interaction between the Saginaw River as a main pollution source and Lake Huron as a reservoir of high quality water. According to the measured DR, it has been evaluated that the nutrient condition of Saginaw Bay is oligotrophic/mesotrophic level in the present period. The molar ratios of N₂ : TIN were kept constant at both sampling sites and not seriously changed with sampling time. The DR was positively correlated to O₂ consumption rates in the headspace of timecours. Additionally,a negative correlationship between NH⁺₄ and NO^-₃ concentrations in the overlying water was found.