This chapter is devoted to nonlinear programming problems with interval entries. Primarily, we will focus on the problem of computing the range of all optimal values. First, we present a general framework to compute the best and worst-case optimal values. Then, we apply it to particular types of nonlinear programming problems, including convex quadratic programming, posynomial geometric programming, linear fractional programming, linear bilevel programming, and the linear complementarity problem. Note that for such special classes we usually can derive stronger results by deep analysis than by applying a general tool.