  We analyse the general constraints on unified gauge models with spontaneous
CP breaking that satisfy the conditions that (i) CP violation in the quark
sector is described by a realistic complex CKM matrix, and (ii) there is no
significant flavor changing neutral current effects in the quark sector. We
show that the crucial requirement in order to conform to the above conditions
is that spontaneous CP breaking occurs at a very high scale by complex vevs of
standard model singlet Higgs fields. Two classes of models are found, one
consisting of pure Higgs extensions and the other one involving fermionic
extensions of the standard model. We give examples of each class and discuss
their possible embeddings into higher unified theories. One of the models has
the interesting property that spontaneous CP violation is triggered by
spontaneous P violation, thereby linking the scale of CP violation to the
seesaw scale for neutrino masses.
