  The nature of finite temperature transitions in lattice QCD with Wilson
quarks is studied near the chiral limit for the cases of 2, 3, and 6 flavors of
degenerate quarks ($N_F=2$, 3, and 6) and also for the case of massless up and
down quarks and a light strange quark ($N_F=2+1$). Our simulations mainly
performed on lattices with the temporal direction extension $N_t=4$ indicate
that the finite temperature transition in the chiral limit (chiral transition)
is continuous for $N_F=2$, while it is of first order for $N_F=3$ and 6. We
find that the transition is of first order for the case of massless up and down
quarks and the physical strange quark where we obtain a value of
$m_\phi/m_\rho$ consistent with the physical value. We also discuss the phase
structure at zero temperature as well as that at finite temperatures.
