In an attempt to show arthrotropic activity for an adenovirus isolated from tenosynovitis in chickens, but which did not cause tenosynovitis on its own, two dual infections were conducted. In the first, specific pathogen-free (SPF) chicks were infected with a tenosynovitis-inducing reovirus at 1-day-old, and the adenovirus was given 3 days later. In both cases viruses were administered orally or via the footpad. The adenovirus did not exacerbate reovirus-induced lesions of tenosynovitis. There was an indication that lesions regressed more rapidly in dually-infected chickens. Neither virus appeared to influence the persistence of the other in joints or the gut. In a second experiment, infectious bursal disease virus (IBDV) was inoculated onto the conjunctiva of 1-day-old SPF chicks and 6 days later they were infected with the adenovirus by either route. No tenosynovitis occurred, although preinfection with IBDV caused a more prolonged shedding of adenovirus, and in a greater proportion of the birds than those infected with adenovirus alone. In neither experiment did the dual infection cause the adenovirus to become pathogenic for the hock joints. It is considered that there is no evidence that adenoviruses are important agents of hock disorders in the chicken.