We report here on the recent &bgr;‐decay studies made at ISOLDE/CERN to determine the multiparticle breakup mechanism of excited states in light nuclei. The &bgr;‐2p emission in31Ar is resolved. Mirror beta transitions in the A=9 chain are compared and a large asymmetry factor is deduced for the transitions to high excitation energy in9Be (11.8 MeV) and9B (12.2 MeV) fed in the &bgr;‐decay of9Li and9C respectively. It is shown that the asymmetry is not due to experimental problems or differences in the mechanisms of breakup or in the spin of the states, only differences in the partial decay branches of the breakup channels has been found. © 2003 American Institute of Physics