Bright 1667 MHz OH maser emission is observed in the nuclear regions of some luminous infrared galaxies. These OH megamaser galaxies are promising tracers of dust-obscured star formation and galaxy mergers at high redshift. Ultimately, these objects could be used to estimate the merger rate as a function of redshift. However, to use OH megamasers as high-redshift probes, a better understanding of the triggering mechanism is needed, for example, whether there is a specific type or stage of merger that produces OH megamaser emission. The onset is likely governed by the physical, chemical and kinematic conditions in the molecular gas in the nuclei of mergers. I will discuss the current understanding of the triggering of OH megamasers.