Bilevel programming problems are optimization problems where the feasible set is implicitly determined by the graph of a (second, parametric) optimization problem, called the lower level problem. To solve them it is necessary to replace this graph using either the Karush-Kuhn-Tucker conditions of the lower level problem, the optimal value function of this problem or some generalized equation. In the talk these problems are formulated, the relations between them as well as related necessary optimality conditions are described.