<p>The region between Jupiter and Saturn in the solar system—where only asteroids with large eccentricities have been discovered—has been studied for prograde orbits in recent years. Investigations of periodic orbits moving there show the structure of the phase space for all kinds of eccentric orbits. Some of these faint objects are in retrograde orbits, and therefore, the next step to study this region between the two most massive planets has been undertaken in the present article. The dynamical model was on one hand the three-dimensional circular restricted three-body problem and on the other hand the same model with Jupiter on an elliptic orbit. Massive numerical integrations for retrograde asteroids between 90 and 180 degrees on initially almost circular orbits have been undertaken for a global picture (1st run) and also on a finer grid (2nd run) in there. The stability was directly checked during the integrations for 10 myr with the aid of the eccentricity. The respective stability diagrams for the 1st run comparing the two mentioned models already show the big difference for taking into account Jupiter’s elliptic orbit. The 2nd run revealed that especially in mean motion resonances the differences are very well visible. Because of these results, it turned out that one should at least use the elliptic problem as a model for the dynamics of the solar system in this interesting domain between Jupiter and Saturn. A more realistic model is the restricted four-body problem where the effect of Saturn is taken into account; this 3rd run revealed big unstable domains in the region between Jupiter and Saturn.</p>