Reductions of the self-duality equation of the Yang-Mills model in d=4
in terms of the action of continuous symmetry groups lead to systems
of differential equations in a lower dimensionality. An algorithm is w
ritten for reducing a Lax pair for self-duality equations with respect
to an arbitrary subgroup of the conformal transformation group of R4
space. The compatibility condition for the reduced Lax pair is shown t
o be the same as the self-duality equations reduced in terms of the ac
tion of the same symmetry group. The general scheme is illustrated wit
h three examples.