This book deals with the mathematical aspects of the derivation of the equations in the kinetic theory of systems of interacting particles from Newtonian mechanics. The first part of the book deals with the derivation of the BBGKY hierarchy from the Liouville equation. An existence theory is developed for the solution to the initial value problem for the hierarchy equations. The second part of the book deals with the derivation of the Boltzmann equation in the Boltzmann grad limit for the hierarchy. The final part of the book is devoted to discrete kinetic theory - the derivation of equations and existence theory.