The aim of this paper is to investigate the stabilizability problem fo
r composite stochastic systems and to apply the results to partially l
inear composite stochastic systems. In particular, we state sufficient
conditions under which there exists a feedback law which renders the
equilibrium solution of the closed-loop system deduced from a composit
e stochastic system exponentially stable in mean square. In the case o
f partially linear composite stochastic systems, the stabilizing feedb
ack law is linear and is related to the solution of a stochastic Ricca
ti-type equation.