Physical maps were established for seven genome types of the intermediate adenovirus (AV) 15/H9 and for the serologically related prototypes AV15 and 9 using the enzymes BamHI, BglII, and HindIII. The polarity of the fragment order was determined by hybridization with known AV2 fragments. AV15/H9 strains showed more restriction sites in common with AV9 than with AV15. The results are consistent with the hypothesis that intermediate AV15/H9 strains have emerged by recombination.