Abstract Autoionization is an important pathway for the relaxation of electronically excited states. In weakly bonded matter, efficient autoionization channels have been found, in which not only the initially excited state, but also neighbouring atoms or molecules take part. Since their theoretical prediction in 1997 these processes are known as interatomic or intermolecular coulombic decay (ICD). The author summarizes the experimental research on ICD up to the presence. Experiments on inner valence ICD in rare gas clusters, on cascade ICD after Auger decay and on ICD of satellite states are explicitly discussed. First experiments on water clusters and on solutes will be reviewed. An outlook on other non-local autoionization processes and on future directions of ICD research closes the article.