  Despite the apparent simplicity of meson spectroscopy there are some states
which cannot be accommodated in the usual $q\bar q$ structure. Among them there
are either exotic states as the X(1600) or the recently measured charm states
$D_{sJ}^*$ and X(3872) and some of the light scalar mesons. In this work we
present a possible description of these states in terms of tetraquarks.
