We generalize the analytical expressions for the two-loop leading-log
neutral Higgs boson masses and mixing angles to the case of general le
ft- and right-handed soft supersymmetry breaking stop and sbottom mass
es and left-right mixing mass parameters (m(Q), m(U), m(D), A(t), A(b)
) This generalization is essential for the computation of Higgs masses
and couplings in the presence of light stops. At high scales we use t
he minimal supersymmetric standard model effective potential, while at
low scales we consider the two-Higgs doublet model (renormalization g
roup improved) effective potential, with general matching conditions a
t the thresholds where the squarks decouple. We define physical (pole)
masses for the top quark, by including QCD self-energies, and for the
neutral Higgs bosons, by including the leading one-loop electroweak s
elf-energies where the top/stop and bottom/sbottom sectors propagate.
For m(Q) = m(U) = m(D) and moderate left-right mixing mass parameters,
for which the mass expansion in terms of renormalizable Higgs quartic
couplings is reliable, we find excellent agreement with previously ob
tained results.