  Gauge mediation of supersymmetry breaking in the observable sector is an
attractive idea, which naturally alleviates the flavour changing neutral
current problem of supersymmetric theories. Quite generally, however, the
number and quantum number of the messengers are not known; nor is their
characteristic mass scale determined by the theory. Using the recently proposed
method to extract supersymmetry-breaking parameters from wave-function
renormalization, we derived general formulae for the soft
supersymmetry-breaking parameters in the observable sector, valid in the small
and moderate $\tan\beta$ regimes, for the case of split messengers. The full
leading-order effects of top Yukawa and gauge couplings on the soft
supersymmetry-breaking parameters are included. We give a simple interpretation
of the general formulae in terms of the renormalization group evolution of the
soft supersymmetry-breaking parameters. As a by-product of this analysis, the
one-loop renormalization group evolution of the soft supersymmetry breaking
parameters is obtained for arbitrary boundary conditions of the scalar and
gaugino mass parameters at high energies.
