This PhD-thesis reviews matrix string theory and recent developments therein. Emphasis is put on symmetries, interactions and scattering processes in the matrix model. We start with an introduction to matrix string theory and a review of the orbifold model that flows out of matrix string theory in the strong YM coupling limit. Then we turn our attention to the appearance of U-duality symmetry in gauge models, after a (very) short summary of string duality, D-branes and M-theory. The last chapter reviews matrix string interactions and scattering processes in the high energy limit. Also, pair production of D-particles is studied in detail. D-pair production is expected to give important corrections to high energy scattering processes in string theory.