Response curves of a tracer step increase and decrease were derived and used to evaluate liquid flow non-idealities and hold-up in a bench-scale reactor by the axial dispersion model. Real feeds and operating conditions used in catalytic hydrotreatment were employed in experimentation. Diluted and non-diluted beds were prepared with non-porous extrudates of commercial catalyst dimensions and crushed particles. Three types of boundary conditions were tested to estimate axial dispersion coefficients and hold-up. The dependence of D-Z and h(L) on the bed particle size and liquid velocity is examined. Bo was found to be a function of bed characteristics.