The Manhattan strain of canine adenovirus type 2 (CAV 2) was examined. Restriction endonuclease analysis and blot hybridization experiments revealed the heterogeneity of the viral DNA. At least 9 unequally expanded species of the viral genome have been recognized. This diversity is caused by different enlargements in the right inverted terminal repeat (ITR) of the virus. The differences between the individual enlargements were shown to be the different multiples of 150 base pairs. Relatedness of CAV 2 DNA to the DNA of bovine adenovirus type 2 (BAV 2) and human adenovirus type 2 (HAV 2) has also been observed during DNA hybridization experiments.