  New approaches to the study of stability of solutions of Set Differential
Equations (SDEs) based on convex geometry and the theory of mixed volumes were
proposed. The stability of the forms of program solutions of linear SDEs with a
stable operator was proved. We consider the orbit of the action of homotheties
group on the space of nonempty convex compacts ($\conv\Bbb R^n$) as the form of
a convex compact. For equations with periodic operator in the two-dimensional
space the asymptotic stability conditions were established.
