Herpesviruses may cause substantial complications after lung transplantation. Especially their interaction with lung tissue cells may result in adverse effects for the transplant patients, and may lead to severe end organ disease or to chronic transplant rejection and to development of bronchiolitis obliterans (BOS). However, the determination of the patients' local virus replication in the lung is still problematic. While the virus load in blood can be easily quantified nowadays, the determination of the virus load in the lung compartment can not be easily achieved, especially due to the individually different and not predictable dilution of virus during sampling of the bronchoalveolar lavage (BAL). In the following a short overview will be given about the different herpesviruses and their possible influence on the transplanted lung as well as about a method to determine the original virus load at the air surface of the lung. The quantitative data achieved by this method underline that some herpesviruses are often present at much higher levels at the air surface of the transplanted lung than in the blood, and that their influence on transplant survival may have been substantially underestimated so far.