In minisum multifacility location problems one has to find locations for several new facilities such that the total interaction cost between all the new as well as between the new and some old facilties given is minimized. Due to its inherent nondifferentiability, this problem is considered as hard to solve. In this thesis, a concept for reducing the complexity of the problem is proposed. The number of unknowns and the number of terms nondifferentiable in a minimum of the objective function can be reduced simultaneously by considering so-called attraction conditions. These attraction conditions are formulated for problems with attracting and repelling facilities and in which several different distance concepts are used simultaneously. It is shown that all other attraction conditions known in the literature can be derived as special cases from the conditions proposed here. Moreover, a polynomial time complexity algorithm is derived for checking these conditions. Numerical results confirm that in this way the computation time for solving a problem is decreased, while simultaneously the quality of the solution computed is increased. Furthermore, a scheme for modeling location problems in inhomogeneous spaces with or without barriers to travel and the numerical treatment of problems of this type is proposed.