The approximate rates and stoichiometries of the reaction of lithium borohydride, with fifty two selected organic compounds containing representative functional groups under the standard condition (tetrahydrofuran, $0^{circ}$), were studied.Among the active hydrogen compounds,primary alcohols and compounds containing an acidic proton liberated hydrogen relatively fast, but secondary and tertiary alcohols very sluggishly. All the carbonyl compounds examined were reduced rapidly within one hour. Especially, among the ${alpha}{eta}$-unsaturated carbonyl compounds tested, the aldehydes consumed one hydride cleanly, however the cyclic ketones consumed more than one hydride even at $-20^{circ}$. Carboxylic acids were reduced very slowly, showing about 60% reduction in 6 days at $25^{circ}$, however acyl chlorides reduced immediately within 30 minutes. On the other hand, the reductions of cyclic anhydrides proceeded moderately to the hydroxy acid stage, however the further reductions were very slow. Aromatic and aliphatic esters, with exception of the relatively moderate reduction of acetate, were reduced very slowly, however lactones were reduced at a moderate rate. Epoxides reacted slowly, but amides and nitriles as well as the nitro compounds were all inert to this reagent. And cyclohexanone oxime and phenyl isocyanate were reduced very sluggishly. Last of all, all sulfur compounds studied were inert to this hydride.