  We analyze the forward-backward asymmetry of the decays B to (pi,K) l^+ l^-
with l = mu or tau in the framework of the constrained minimal supersymmetric
standard model. We find that, the asymmetry is enhanced at large tan beta and
depends strongly on the sign of the mu parameter. For mu > 0, the asymmetry is
typically large and observable whereas for mu < 0, it changes the sign and is
suppressed by an order of magnitude. Including cosmological constraints we find
that the asymmetry has a maximal value of about 30 %, produced when Higgs- and
gauge- induced flavor violations are of comparable size, at a value of tan beta
simeq 35. The present constraints from the B-factories are too weak to
constrain parameter space, and the regions excluded by them are already
disfavoured by at least one of B to X_s gamma, g-2, and/or cosmology. The size
of the asymmetry is mainly determined by the flavor of the final state lepton
rather than the flavor of the pseudoscalar.
