Existing bridges with large uncertainties can be assessed with proof load tests, hi such tests, a load representative of the factored live load is applied to the structure. If the bridge can cany the load without any signs of distress or nonlinearity, the test is considered successful. Since large loads are applied in proof load tests, the monitored structural responses are used to define stop criteria. This paper presents stop criteria for shear and flexural failure based on existing codes and guidelines and theoretical considerations. The proposal is verified with the available information from previous tests 011 reinforced concrete beams, the pilot proof load tests and a collapse test earned out in the Netherlands. The results are that the stop criteria are not exceeded and therefore, the proposed stop criteria can be used for proof load tests. However, further experimental validation is needed, especially for shear failure.