  Weak decays of heavy flavored hadrons are sensitive probes of several facets
of the Standard Model. In particular the experimental study of B meson
semileptonic decaysis starting to pin down the quark mixing parameters in the
Cabibbo Kobayashi Maskawa matrix. In addition, some features of the
non--perturbative regime of the strong interaction are probed by these decays.
New results from the CLEO experiment at the CESR electron-positron collider,
based on a data sample of up to 3.5 inverse femtobarn, provide crucial
information on both of these aspects of heavy flavor phenomenology.
