Sixteen fatal cases of adenovirus infection in infants (n:10 aged 1 to less than 12 months) and children (n:6 aged 1 to 3, 8/12 years) are reported. Diagnosis were confirmed by direct viral isolation, viral immunofluorescence or both in 15 patients, and by autopsy in 12 of them, including one without positive virological workup. Evidence of multisystemic compromise, particularly that of severe lower respiratory tract infection was observed and lead to death by acute respiratory failure in all cases. White blood cell counts and erythrocyte sedimentation rate did not help to label initially the etiology as either viral or bacterial. Chest roentgenograms showed pulmonary over-inflation and evidence of pneumonitis as well as extensive and rapidly progressive lung opacifications. Most prominent pathologic findings were necrotizing bronchitis, bronchiolitis and broncopneumonia. Several cells containing typical intranuclear inclusion bodies were documented in ten cases and pneumonitis was the only finding in two. Hepatic fat infiltration and lymphocitic depletion of thymus, spleen and lymphatic nodes occurred in all cases. The need of rapid diagnostic tools to avoid nosocomial spread of this kind of infections with such serious consequences is stressed.