Let $A$ be an Azumaya $C$-algebra. Then the set of all
commutative separable subalgebras of $A$ and the set of separable subalgebras
$B$ such that $V_A(B)=V_B(B)$ are in a one-to-one correspondence, where
$V_A(B)$ is the commutator subring of $B$ in $A$, and the set of all separable
subalgebras of $A$ is a disjoint union of the Azumaya algebras in $A$ over a
commutative separable subalgebra of~$A$. The results are used to compute
splitting rings for an Azumaya skew group ring.
Keywords: Azumaya algebras, Galois
extensions, splitting rings, skew group rings.