Adenovirus 3 was found associated with ten cases of infantile lower acute respiratory infection in patients aged 2-18 months. Of these, five had a fatal outcome, with severe lung damage. Restriction enzyme analysis with Bam HI, Bcl I, Bgl II, Bst E II, Hind III, Sal I, Sma I, Xba I, and Xho I revealed the presence of the same genome type in all ten specimens. The genomic variant was different from those previously reported for serotype 3 and therefore was tentatively denominated 3f.