Connections between inclusive and exclusive semileptonic B decay

B decay sum rules relate exclusive B semileptonic decay matrix elements to forward B-meson matrix elements of operators in HQET. At leading order the operators that occur are the b-quark kinetic energy {lambda}{sub 1} and chromomagnetic energy {lambda}{sub 2}. The latter is determined by the measured B{sup {asterisk}}{minus}B mass splitting. The derivation of these sum rules is reviewed and perturbative QCD corrections are discussed. A determination of {lambda}{sub 1} and the energy of the light degrees of freedom in a B-meson, {bar {Lambda}}, from semileptonic B decay data is presented. Future prospects for improving these sum rules are discussed. {copyright} {ital 1997 American Institute of Physics.}