We present a study of the two species totally asymmetric diffusion model
using the Bethe ansatz. The Hamiltonian has Uq(SU(3)) symmetry. We derive
the nested Bethe ansatz equations and obtain the dynamical critical exponent
from the finite-size scaling properties of the eigenvalue with the smallest
real part. The dynamical critical exponent is 3/2 which is the exponent
corresponding to KPZ growth in the single species asymmetric diffusion model