Studies of lung tissues and bronchoalveolar lavage specimens from patients with pneumonia have led some investigators to propose that human herpesvirus 6 (HHV-6) can cause pneumonia. As the etiologic role of HHV-6 in pneumonia remains poorly defined, cases of pneumonia that are associated with pulmonary HHV-6 infection are best described as HHV-6-associated pneumonias. The clinical spectrum of HHV-6-associated pneumonia encompasses both mild and severe cases. Most cases reported so far occurred in immunosuppressed individuals following bone marrow transplantation or HIV infection. Some studies have identified coinfections with HHV-6 and other viruses in a surprising number of HHV-6-associated pneumonias. Although no systematic evaluation of treatment regimens is available at this time, coincidental administration of antiviral drugs did not generally result in clinical improvement. Controlled, prospective studies are needed to understand the clinical presentation, clinical course, etiology, diagnosis and treatment of HHV-6-associated pneumonias.