Background and objective: Bosentan, an oral, dual endothelin receptor antagonist, significantly improves functional status, haemodynamic measures and survival in patients with pulmonary arterial hypertension (PAH). However, there are limited data on the effect of bosentan on quality of life (QOL) and its relationship to changes in functional status, as measured by the 6 minute walk distance (6MWD).Methods: A retrospective analysis was performed of a large, open-label, multicentre trial (VITAL) of bosentan in patients with PAH. Data for 6MWD were collected at baseline, 3 or 6 months and these results were correlated with QOL measurements collected as part of the assessment of patients enrolled in the trial.Results: Sixty-nine patients with PAH (mean age 52 years) who were enrolled in the trial had valid QOL (SF-36) measurements and 6MWD data that could be retrieved from clinical notes. At 3 and 6 months, bosentan therapy improved 6MWD compared with baseline (49.5 m and 47.2 m, respectively, P <0.001) as well as QOL domains, with a significant correlation between these two markers on cross-sectional analysis. However, there was a poor relationship when comparing changes in 6MWD with changes in QOL, in response to therapy.Conclusion: Bosentan therapy was associated with improvements in QOL and 6MWD for at least 6 months. At all measured time points, there was a close correlation between 6MWD and most QOL domains. QOL is an important parameter and should be considered as part of the standard assessment for any trial investigating therapy in PAH.