This report is concerned with acute exudative tonsillitis as a pathologic response to the Epstein-Barr virus (EBV). The concept of a bacterial-viral etiology etiology for tonsillitis has been suggested, and previous studies implicate EBV as a major pathogen in exudative tonsillitis. A prospective study of 16 patients with this diagnosis was conducted. EBV serologic data plus viral and bacterial throat cultures were compiled and evaluated. EBV as a casual agent alone or concurrent with other organisms was seen in 56% (9) of the patients under study. EBV activation was associated with infection by other organisms in 19% (3) of the cases. The overall total incidence of EBV in association with severe acute exudative tonsillitis was 75% (12). The data further documents EBV as a significant causal or associative agent in acute exudative tonsillitis.