IT was shown by Kapsenberg1 and Heller and Salenstedt2 that infectious canine hepatitis virus (ICH) and adenoviruses possessed common complement fixing antigens. Heller and Salenstedt2 demonstrated five precipitin lines in Ouchterlony plates in the reaction between ICH and convalescent serum from a dog infected with ICH. Three of the antigens forming these precipitin lines were common to adenovirus type 7 which itself gave five precipitin lines with human anti-adenovirus type 7 convalescent serum. The immunological relationship between the two viruses was one-sided, as anti-adenovirus type 7 serum would react in Ouchterlony plates with ICH, but anti-ICH would not react with adenovirus type 7. Recently, Darbyshire and Pereira3 have demonstrated two antigens in the livers of ICH infected dogs which can be precipitated with dog anti-ICH. One of these antigens is precipitated by rabbit anti-adenovirus type 5 serum. In the experiments reported here it was found that ICH infected dog kidney cultures produced only two soluble viral antigens, one of which is closely similar to the A (group specific) antigen of adenoviruses types 5 and 7 and another which is specific for ICH.