Some features of a program  eett6f for top quark pair production and decay into six fermions at linear colliders are discussed. Lowest order standard model predictions for cross sections of some six fermion channels and for the top quark decay width are confronted with the predictions obtained within a model with an anomalous Wtb coupling. The question of whether non doubly resonant background can easily be reduced by imposing kinematical cuts is addressed.

PACS numbers: 12.15.-y, 13.40.Ks, 14.65.Ha