  The rare exclusive dileptonic $\Lambda_{b}\to \Lambda\ell^{+}\ell^{-}$ $(\ell
=\mu, \tau)$ decays are investigated in the general two-Higgs-doublet model of
type III. A significant enhancement to the branching ratios, differential
branching ratios, leptons forward-backward asymmetry, and the $\Lambda$ baryon
polarizations over the standard model is obtained. Measurements of these
quantities will be useful for establishing the two-Higgs doublet model.
