A method for providing an adenovirus from a serotype which does not grow efficiently in a desired cell line with the ability to grow in that cell line is described. The method involves replacing the left and right termini of the adenovirus with the corresponding termini from an adenovirus which grow efficiently in the desired cell line. At a minimum, the left terminus spans the 5' inverted terminal repeat, the left terminus spans the E4 region and the 3' inverted terminal repeat. The resulting chimeric adenovirus contains the internal regions spanning the genes encoding the penton, hexon and fiber from the serotype which does not grow efficiently in the desired cell. Also provided are vectors constructed from novel simian adenovirus sequences and proteins, host cells containing same, and uses thereof.