This invention provides methods of selecting antibodies that are internalized into target cells. The methods generally involve contacting target cells with one or more members of an antibody phage display library. The members of the phage display library are also contacted with cells of a subtractive cell line. The target cells are then washed to remove the subtractive cell line cells and members of the phage display library that are non-specifically bound or weakly bound to the target cells. The target cells are cultured under conditions where members of the phage display library can be internalized if bound to an internalizing marker and internalized members of the phage display library are then identified.