The human adenoviruses comprise 51 distinct serotypes that are grouped into six subgroups (A to F) based on various immunologic, biological, and biochemical characteristics. The infection cycle takes approximately 30 h in tissue culture cells and results in the production of approximately 50,000 to 100,000 new virus particles per cell. The infectious cycle can be divided into four stages: entry, early events, late events, and virus assembly. Chloramine-T (p-toluenesulfonchloramide) at 5% for 15 min or at 0.6% for 30 min or 500 ppm of sodium hypochlorite for 10 min can be used to inactivate adenoviruses. Phenylmercuric borate, isopropyl alcohol, ether, cetrimide, and chlorhexidine gluconate do not inactivate adenoviruses. Approximately 10 to 20% of childhood pneumonias are attributed to adenoviruses. Adenoviral pneumonia in military conscripts was originally classified as atypical pneumonia until the viral etiology was discovered. Clinically and radiologically adenoviral pneumonia may resemble Mycoplasma pneumoniae pneumonia. Recent observations on detection of adenoviruses by PCR in air and on surfaces suggest that proper cleaning, isolation of patients with suspected or confirmed cases of adenovirus infection, and restriction of new admissions may be essential in limiting the risk of nosocomial spread. At present there is no specific antiviral treatment of proven value for adenovirus infections. Ribavirin, ganciclovir, and cidofovir are variably active against adenoviruses in vitro and thus potentially effective for treatment.