  We study the semileptonic decays of double heavy baryons using a manifestly
Lorentz covariant constituent three-quark model. We present complete results on
transition form factors between double-heavy baryons for finite values of the
heavy quark/baryon masses and in the heavy quark symmetry limit which is valid
at and close to zero recoil. Decay rates are calculated and compared to each
other in the full theory, keeping masses finite, and also in the heavy quark
limit.
