The present invention provides formulations for maintaining the stability of Ap binding polypeptides, for example. Ap antibodies. Exemplary formulations include a tonicity agent such as mannitol and a buffering agent or amino acid such as histidine. Other exemplary formulations include an antioxidant in a sufficient amount as to inhibit by-product formation, for example, the formation of high molecular weight polypeptide aggregates, low molecular weight polypeptide degradation fragments, and mixtures thereof. The formulations of the invention optionally comprise a tonicity agent, such as mannitol, and a buffering agent or amino acid such as histidine. The formulations are suitable for several different routes of administration.
