A large subset of the Dutch bridge stock consists of reinforced concrete slab bridges, for which assessment often results in low ratings. To prioritize the efforts of the bridge owner, more suitable assessment methods for slab bridges are necessary. Research efforts over the past years resulted in the development of several methods, at levels requiring increasing costs, time, and effort for increasing accuracy. The last option, when an analytical assessment is not possible due to uncertainties, is to use proof load testing to evaluate the bridge directly. To develop recommendations for the proof load testing of reinforced concrete slab bridges for the Netherlands, different methods are combined: pilot proof load tests on bridges with and without material damage, a collapse test, tests on beams taken from an existing bridge and new beams with similar dimensions cast in the laboratory, and an extensive literature review. The result of this study is a set of recommendations that describe how to prepare and execute a proof load test, and how to analyze the results. This paper summarizes the research program about proof load testing from the Netherlands and gives an overview of the currently developed recommendations and topics for further research.