The enteric adenoviruses of subgroup F (Ad40 and Ad41) pose some special problems of cultivation, as they cannot be readily passaged in many of the cell types used to propagate the more commonly used subgroup C serotypes (Ad2 and Ad5), and there is no standard plaque assay: A full discussion of the observations from many laboratories is included in a recent review (1). For the purposes of this chapter, I will describe the methods developed in my laboratory to passage Ad40 in 293 and KB16 cells, to assay the virus by a variety of methods, to purify the virus by cesium chloride density gradient centrifugation, and to obtain viral DNA. Most of the methods have been derived from those developed for Ad5, but with constraints imposed by the more fastidious nature of the enteric adenoviruses.