The paper presents the results and experiences derived from a series of proof load test on concrete bridge structures. There are three main parts of the paper. The first part is a theoretical part related to the assessment of the target values of the proof load tests. The load level in the test necessary to guarantee a predefined safety level under real traffic conditions can be obtained in a reliability-based methodology with two different approaches depending on if data is available or not for the bridge under evaluation. The second part is an evaluation of the measurements results during static loading. The important element is the correct and accurate estimation of the elastic and permanent values of measured quantities taking into account their speed of stabilization. The third part is connected with an incremental loading and is about estimation of the time when the bridge materials approach their elastic limit during incremental loading and therefore, the test should stop.