Samples of lung tissue, taken at time of lung transplant, from 13 Dutch Caucasian patients with idiopathic pulmonary arterial hypertension (iPAH) and 14 patients with non-idiopathic PAH were studied for the presence of human herpes virus-8 (HHV-8). By immunohistochemical staining, in none of patients expression of HHV-8 latency-associated nuclear antigen 1 (LANA-1) was demonstrated. Using two nested polymerase chain reactions (PCR) to amplify part of the open reading frame (ORF) 65 and ORF 73, we failed to detect HHV-8 DNA in all samples studied. These results argue strongly against a role for HHV-8 in the pathogenesis of iPAH.