  We study phase transitions and the behavior of kaons in hot and dense matter,
giving special attention to the role of strange quarks. At T=0, it is found
that the fraction of the strange valence quarks affects the energy per particle
of the system, without changing the nature of the phase transition, and, on the
other side, it has meaningful effects on the behavior of kaons and antikaons
masses. The phase behavior of kaons in the $T-\rho$ plane is analyzed in
connection with the chiral phase transition.
