Since the end of the last century many investigations have been carried out concerning the question if stresses due to the tidal forcing of the earth do trigger earthquakes or volcanic activities. Since the publications are so numerous and the results so controversial a complete review is impossible. An attempt is made to describe the different methods of investigation applied in most of the searches for tidal triggering. Summaries of the most important papers and their results are given separately for the different types of geophysical events such as earthquakes, volcanic eruptions and volcanic shocks.