This chapter develops a new approach to a class of hybrid optimal control problems of the Mayer type. Hybrid control systems are mathematical modes of heterogeneous systems consisting of a continuous part, a finite number of continuous controllers and a discrete supervisor. For a hybrid optimal control problem, the main tool toward the construction of optimal trajectories is the Hybrid Maximum Principle. This approach is based on explicit formulae for the reduced gradient of the cost functional of the given hybrid optimal control problem. The corresponding relations make it possible to formulate first-order necessary optimality conditions for the considered hybrid optimal control problems and provide a basis for effective computational algorithms. The idea of reduced gradients can also be used for some linearization procedures of the initial optimal control problem, the main tool toward the construction of optimal trajectories is the Hybrid Maximum Principle. © 2006 Elsevier Ltd All rights reserved.