  A quasiclassical theory of giant magnetoresistance in nanoscale point
contacts between different ferromagnetic metals is developed. The contacts were
sorted by three types of mutual positions of the conduction spin-subband
bottoms which are shifted one against another by the exchange interaction. A
model of linear domain wall has been used to account for the finite contact
length. The magnetoresistance is plotted against the size of the nanocontact.
In heterocontacts the magnetoresistance effect turned out to be not only
negative, as usual, but can be positive as well. Relevance of the results to
existing experiments on GMR in point heterocontacts is discussed.
