V.E.Chernyshev Heteroclinic contours that generate stable chaos Summary A new class of invariant sets of relatively simple structure is investigated. This class consists of heteroclinic cycles of the Lorenz type. It is shown that if a three-dimensional autonomous system of differential equations has an invariant set of this class, then the system exhibits chaotic behavior of trajectories in a neighborhood of this set. This chaotic behavior is not destroyed by $C^1$ small perturbations, only its topological structure is changed. Possible bifurcations of the chaotic invariant set generated by a heteroclinic cycle of the Lorenz type are described. Russian, 208 pp.; an English version of the Introduction (8 pp.). AMS classification (AMS2000) Primary: 37D45 Secondary: 37C29, 37G30, 34C28, 34C37