  The effects of structural (Rashba) and bulk (Dresselhaus) spin-orbit
interaction terms on the low-field magnetoresistance are investigated in
high-quality two dimensional systems. The weak localization theory accounting
for both of these terms valid in the whole range of magnetic fields is
proposed. The suppresion of antilocalization correction as Rashba and
Dresselhaus terms strengths approach each other is demonstrated. The effect of
cubic in the wavevector spin-splitting term is analyzed.
