The question of the integrability of real-coupling affine toda field t
heory on a half-line is addressed. It is found, by examining low-spin
conserved charges, that the boundary conditions preserving integrabili
ty are strongly constrained. In particular, for the a(n) (n > 1) serie
s of models there can be no free parameters introduced by the boundary
condition; indeed the only remaining freedom (apart from choosing the
simple condition partial derivative 1phi = 0), resides in a choice of
signs. For a special case of the boundary condition, it is argued tha
t the classical boundary bound state spectrum is closely related to a
consistent set of reflection factors in the quantum field theory.