[1] Field measurements and incubation techniques were used to determine the dynamics of acetate formation, iron reduction, and methanogenesis in surficial peat of an Alaskan bog. Acetate concentrations were $100 mM early in the season and decreased to $20 mM in July when the water table decreased. Acetate levels increased rapidly to $1000 mM when the water table rose to the surface in August. Acetate production in anaerobic slurries occurred at rates of 2.8-420 nmol carbon mL À1 day À1 , which was 7-120 times more rapid than CH 4 production. Experiments utilizing 14 C-acetate confirmed that methanogenesis was not acetoclastic although acetate was converted very slowly to CO 2 . Peat incubated anaerobically for 4.5 months at 24°C never produced methane from acetate, suggesting that anaerobic acetate accumulation would have occurred all season if the water table had remained high. CO 2 production was the most rapid process measured in laboratory incubations (up to 750 nmol mL À1 day À1 ) and appeared to be due primarily to fermentation. Acetate was the primary organic terminal product of anaerobic decomposition in the bog, and acetate was ultimately oxidized to CO 2 via aerobic respiration and to a much lesser extent anaerobically by Fe reduction.