In this review we discuss the evidence for galaxy interactions and mergers in the distant universe and the role of mergers in forming galaxies .
Observations show that the fraction of massive ( M > M _ { * } ) galaxies involved in major mergers is roughly 5-10 % at z \sim 1 .
The merger fraction however increases steeply for the most massive galaxies up to z \sim 3 , where the merger fraction is 50 \pm 20 % .
Using N-body models of the galaxy merger process at a variety of merger conditions , merger mass ratios , and viewing angles this merger fraction can be converted into a merger rate , and mass accretion rate due to mergers .
A simple integration of the merger rate shows that a typical massive galaxy at z \sim 3 will undergo 4-5 major mergers between z \sim 3 and z \sim 0 , with most of this activity , and resulting mass assembly , occurring at z > 1.5 .