  We derive the upper bounds on certain products of R-parity- and
lepton-flavor-violating couplings from $B^\pm \to l^\pm \nu$ decays. These
modes of B-meson decays can constrain the product combinations of the couplings
with one or more heavy generation indices which are comparable with or stronger
than the present bounds. And we investigate the possible effects of R-parity
violating interactions on $B_c \to l \nu$ decays. These decay modes can be
largely affected by R-parity violation.
