High oil maize stover upon removal of ears was ensiled in 3 L volume glass jars for 1, 3, 6, 9 weeks to investigate the effects of buffered propionic acid and propionic acid bacteria on fermentation and aerobic stability of the silage. Treatments were: 1. control (no additives added), 2. buffered propionic acid added at 5 L/t fresh high oil maize stovers, and 3. propionic acid bacteria from Propionibacterium acidipropionici added at 10⁵ cfu/g of fresh high oil maize stovers. The addition of buffered propionic acid and propionic acid bacteria had little effect on final pH or concentrations of total lactic acid and ammonia N. Final concentrations of residual water soluble carbohydrate and propionic acid and the percentage of D-lactic acid of total lactic acid were higher in buffered propionic acid treated silage. Aerobic stability of the silages was investigated after opening the laboratory silo jars at 9 wk postfilling. Silage treated with propionic acid bacteria had more yeasts than other silages after 7 d of aerobic exposure. Molds were only found at 5 d of aerobic exposure in control. Butyric acid was not detected with exception of untreated silage at the end of 7 d of exposure. After 7 d of aerobic exposure, pH of control increased from 3.39 to 5.30, while the corresponding pH values were increased from 3.5 to 4.11 in propionic acid bacteria and from 3.56 to 3.65 in silage treated with buffered propionic acid. Both buffered propionic acid and propionic acid bacteria used as silage additives improved the aerobic stability of high oil maize stover silage, but buffered propionic acid was more effective.