Polyampholyte are able to condense nucleic acid to form small complexes which can be utilized in the delivery of nucleic acid to mammalian cells. The polyampholytes can be formed prior to interaction with nucleic acid or they can be formed in the presence of nucleic acid. Stabilized polycation/nucleic acid complexes can be modified to reduce the positive charge of the polycation and add targeting ligands without destabilizing the complex. The resultant particles retain their small size and are more effective in delivery of nucleic acid to cells in vivo.