  SU(3) breaking in hyperon semi-leptonic decays is discussed. The SU(3)
parameters $F$ and $D$, relevant to the ``proton-spin puzzle'', are extracted
and a prediction is presented for the decay Xi0 -> Sigma+ e anti-neutrino,
currently under study by the KTeV collaboration. The values found are g1/f1 =
1.16+/-0.03+/-0.01 and Gamma = (0.80+/-0.03+/-0.01) x 10^6 s^-1.
