  The issue of asymmetric uncertainties resulting from fits, nonlinear
propagation and systematic effects is reviewed. It is shown that, in all cases,
whenever a published result is given with asymmetric uncertainties, the value
of the physical quantity of interest is biased with respect to what would be
obtained using at best all experimental and theoretical information that
contribute to evaluate the combined uncertainty. The probabilistic solution to
the problem is provided both in exact and in approximated forms.
