We consider some repulsive multimarginal optimal transportation problems which include, as a particular case, the Coulomb cost. We prove a regularity property of the minimizers (optimal transportation plan) from which we deduce existence and some basic regularity of a maximizer for the dual problem (Kantorovich potential). This is then applied to obtain some estimates of the cost and to the study of continuity properties.This problem is called a multimarginal optimal transportation problem and elements of Π(ρ) are called transportation plans for ρ. Some general results about multimarginal optimal transportation problems are available in [3,17,21,22,23]. Results for particular cost functions are available, for example in [11] for the quadratic cost, with some generalization in [15], and in [4] for the determinant cost function.Optimization problems for the cost function C(ρ) in (1.1) intervene in the socalled Density Functional Theory (DFT), we refer to [16,18] for the basic theory of DFT and to [13,14,24,25,26] for recent development which are of interest for us. Some new applications are emerging for example in [12]. In the particular case of the Coulomb cost there are also many other open questions related to the applications. Recent results on the topic are contained in [2,5,6,7,10,20] and some of them will