Abstract. The general notion of fully nonlinear second-order elliptic equation is given. Its relation to so-called Bellman equations is investigated. A general existence theorem for the equations like Pm(uxixj) = JJ™^1 ck(x)Pk(uxixj) *s obtained as an example of an application of the general notion of fully nonlinear elliptic equations.We will be dealing with the following question: Given an equation It may look strange that we address such a question. Indeed, there are even books [9], [17] and many articles about the general theory of fully nonlinear elliptic equations. Therefore, very general results are available in the theory. However, on the other hand, it turns out that if an unexperienced reader meets a fully nonlinear second-order partial differential equation in his investigations and tries to get any information about its solvability from the literature, then almost certainly he fails to find what he needs, unless he considers an equation that is exactly one which had already been treated. The point is that in the general theory we consider nonlinear equations only of a special type, say, such that for any x e D, £ e Rd, uij, w,, u e R S\{\2 < F(uij+^,z)-F(uij, z) < S~x\c]\2, where z = (w,, u, x) and S is a positive constant. Obviously, even for the simplest Monge-Ampere equation, when F = det(w,;) -f(x), conditions of this type are not satisfied (for instance, for d > 2 the function det(M,;) grows much faster than linearly). Nevertheless, the general theory applies to this and many other special equations, and the reason for this is that in an appropriate class of functions they can be reduced to those considered in the general theory. We apply some techniques to include into our theory concrete equations such as the Monge-Ampere equation (real or complex) or more general Weingarten equations. These techniques are different in different cases, and by answering our main question here we want to show, in particular, what should be done for