  We consider the problem of Bose condensation of charged pions in QCD at
finite isospin chemical potential $\mu_I$ using the O(4)-symmetric linear sigma
model as an effective field theory for two-flavor QCD. Using the 2PI
$1/N$-expansion, we determine the quasiparticle masses as well as the pion and
chiral condensates as a function of the temperature and isospin chemical
potential in the chiral limit and at the physical point. At T=0, Bose
condensation takes place for chemical potentials larger than $m_{\pi}$. In the
chiral limit, the chiral condensate vanishes for any finite value of $\mu_I$.
