The stability of acetic acid in the presence of excess oxygen is evaluated for a range of vanadium phosphate and oxide catalysts. In the temperature range 300-400 degreesC most oxides catalyse the total oxidation of acetic acid to carbon dioxide and water. However, over molybdenum oxide acetic acid oxidation is not significant. This is consistent with Mo being a major component of oxide catalysts that have, to date, been identified for the selective oxidation of ethane to acetic acid at this temperature. Interestingly, VO(H2PO4)(2), a phase that is very non-selective for the partial oxidation of n-butane, exhibits the highest stability for acetic acid under oxidising conditions. It is proposed that catalysts based on VO(H2PO4)(2) may provide the basis of improved ethane partial oxidation catalysts.