For the domain $R$ arising from the construction $T, M, D$,\ud
we relate the star class groups of $R$ to those of $T$ and $D$.\ud
More precisely, let $T$ be an integral domain, $M$ a nonzero maximal ideal of $T$, $D$ a proper subring of $k:=T/M$, $\varphi: T\rightarrow k$ the natural projection, and let $R={\varphi}^{-1}(D)$.\ud
For each star operation $\ast$ on $R$, we define the star operation\ud
$\ast_\varphi$ on $D$, i.e., the ``projection'' of $\ast$ under $\varphi$, and the star operation ${(\ast)}_{_{\!T}}$ on $T$, i.e., the ``extension'' of $\ast$ to $T$.\ud
Then we show that, under a mild hypothesis on the group of units of\ud
$T$, if $\ast$ is a star operation of finite type, then the sequence of canonical homomorphisms\ud
$0\rightarrow \Cl^{\ast_{\varphi}}(D) \rightarrow \Cl^\ast(R)\ud
\rightarrow \Cl^{{(\ast)}_{_{\!T}}}(T)\rightarrow 0$\ud
is split exact. In particular, when $\ast = t_{R}$, we deduce\ud
that the sequence\ud
$\ud
0\rightarrow \Cl^{t_{D}}(D)\ud
{\rightarrow} \Cl^{t_{R}}(R)\ud
{\rightarrow}\Cl^{(t_{R})_{_{\!T}}}(T) \rightarrow 0\ud
$\ud
is split exact. The relation between ${(t_{R})_{_{\!T}}}$ and\ud
$t_{T}$ (and between $\Cl^{(t_{R})_{_{\!T}}}(T)$ and $\Cl^{t_{T}}(T)$)\ud
is also investigated