Adenovirus, a frequent cause of mild respiratory disease in military trainees, can result in severe manifestations when outbreaks are caused by novel viral strains for which there is little pre-existing immunity. Twenty-five basic military trainees (BMTs) were hospitalized with adenovirus pneumonia from April 1, 2007 through June 21, 2007. Clinical findings for 9 of these patients with PCR-confirmed adenovirus serotype 14 were studied retrospectively. The clinical picture was characterized by cough (88.9%) and sputum production (77.8%). All trainees were febrile. Laboratory results showed 88.9% had normal white blood cell (WBC) counts, 66.7% with high monocytes, and 55.6% with low lymphocytes on differential. All had lobar pneumonia radiographically. One patient required the intensive care unit (ICU) and later expired. In conclusion, among hospitalized patients with the combination of fever, productive cough, normal WBC, a differential showing high monocytes and low lymphocytes in an immunocompetent young adult with lobar pneumonia warrants a high level of suspicion for adenovirus 14 pneumonia.