The present invention relates to methods and compositions for the production of recombinant Adeno-Associated Viruses (rAAV). In particular, the invention discloses nucleic acid constructs and packaging cells having improved properties for rAAV production, as well as novel methods of titration and characterization of rAAV preparations. The invention also describes novel sequences which promote or increase the packaging of nucleic acids in rAAV, and their use for producing rAAV with high efficiency. The invention can be used for producing or testing high quality rAAV preparations, for biological, preclinical, clinical or pharmaceutical uses.