  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. We find that such an interaction binds a heavy
tetraquark system $QQ\bar q\bar q$ ($Q=c, b$ 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.
