  We discuss the stability of multiquark systems within the recent model of
Glozman et al. where the chromomagnetic hyperfine interaction is replaced by
pseudoscalar-meson exchange contributions. We find that such an interaction
binds a heavy tetraquark systems $QQ\bar q\bar q$ ($Q=c,b and q=u,d)$ by
0.2-0.4 GeV. This is at variance with results of previous models where $cc\bar
q\bar q$ is unstable.
