  In this work pion and kaon condensation in the framework of chiral
perturbation theory is studied. I consider a system at vanishing temperature
with nonzero isospin chemical potential and strangeness chemical potential;
meson masses and mixing in the normal phase, the pion condensation phase and
the kaon condensation phase are described. There are differences with previous
works, but the results presented here are supported by both theory group
analysis and by direct calculations. Some pion decay channels in the normal and
the pion condensation phases are studied, finding a nonmonotonic behavior of
the $\Gamma$ decay width as a function of $\mu_I$.
