  We probe the $\theta$-dependence of QCD at finite isospin chemical potential
$\mu_I$ using the effective chiral Lagrangian approach. The phase diagram in
the $\theta$, $\mu_I$ plane is constructed and described in detail in terms of
chiral and pion condensates. The physics at $\theta ~ \pi$ is investigated in
both the normal and superfluid phase. Finally, the behaviour of the gluon
condensate at finite $\mu_I$ is computed.
