To provide the best possible basis for political decision-making, the present study is designed as a nationwide cluster-randomised, controlled trial including general hospitals, university hospitals, and psychiatric hospitals from all five regions in Denmark. The objective of this trial is to evaluate the effect of unannounced hospital surveys based on findings of a survey embracing an abbreviated set of the national accreditation standards and performance indicators from the DDKM version 2. We hypothesise that unannounced surveys produce less successful measures of organisational performance than announced surveys. This study defines less successful as less compliance with the included standards and performance indicators.