This thesis presents an investigation of semileptonic B meson decays with a narrow P-wave charm meson in the final state. The data sample consists of 3.29 x 106 BB¯ events collected with the CLEO II detector at the Cornell Electron-positron Storage Ring. The P-wave charm mesons are reconstructed in the chain of decays: D0J→D*+p- ,D*+→D0p+,D 0→K-p+ or D0→K-p+p 0 . Study of the decay B-→D*+p0ℓ -nℓ&d1; reveals useful information about the deficit observed in inclusive charm semileptonic B decays and the effective couplings of the W boson to heavy quark mesons. The results obtained for the exclusive semileptonic product branching fractions are BB-→D0 1ℓ-nℓ &d1;B D01→D*+p - = (0.373 +/- 0.085 +/- 0.052 +/- 0.024)% and BB-→D*0 2ℓ-nℓ&d1; BD*0 2→D*+p- < 0.16% (90% C.L.). The assumption BD01→D* +p- = 67% and BD*02→D *+p- = 20% implies BB-→D01 ℓ-nℓ&d1; (0.56 0.13 +/- 0.08 +/- 0.04)% and BB-→D*0 2ℓnℓ&d1; < 0.8% (90% C.L.). These results indicate that at least 18% of the total B semileptonic rate is still unaccounted for by the observed exclusive decays, B&d1;→D0ℓ- n&d1;ℓ, B&d1;→D*ℓn &d1;ℓ,B&d1; →D1ℓn&d1; ℓ, and B&d1;→D*2 ℓn&d1;ℓ . Furthermore, the first measurement of the q 2 spectrum for B-→D01ℓn &d1;ℓ is presented. The present analysis also suggests that the Λ QCD/mQ corrections beyond the HQS prescriptions might be significant in the theoretical treatment of the dynamics of B semileptonic decays to excited charm mesons.