Aims: Data on long-term efficacy of bosentan in unselected idiopathic pulmonary arterial hypertension(IPAH) patients are lacking. We aimed to describe the long-term outcome of consecutive IPAH patients treated first-line with bosentan. Methods and results: A retrospective analysis of 103 consecutive New York Heart Association functional class III/IV IPAH patients treated with bosentan at our centre between November 1999 and May 2004 was performed. The 6-minute walk distance(6MWD) and haemodynamics were assessed at baseline and after 4 and 12 months. Mean follow-up was 24±15 months. At 4 months, significant improvements in exercise capacity and haemodynamics were observed and persisted up to 1 year. Overall survival estimates were 90 and 87%and event-free status(survival without transplantation, prostanoid initiation, or hospitalization for right heart failure) estimates were 61 and 44%at 1 and 2 years, respectively. Forty-five(44%) patients required prostanoid therapy during follow-up. The 6MWD and the right atrial pressure at baseline and the 6MWD, the increase in 6MWD, and the decrease in pulmonary resistance after 4 months of treatment were associated with long-term outcomes. Conclusion: In our series of consecutive IPAH patients treated with bosentan, improvements in exercise capacity and haemodynamics were similar to those observed in previous randomized trials. However, on the basis of local criteria, many patients required the addition of prostanoid therapy during follow-up. Aims: Data on long-term efficacy of bosentan in unselected idiopathic pulmonary arterial hypertension (IPAH) patients are lacking. We aimed to describe the long-term outcome of consecutive IPAH patients treated first-line with bosentan. Methods and results: A retrospective analysis of 103 consecutive New York Heart Association functional class III / IV IPAH patients treated with bosentan at our center between November 1999 and May 2004 was performed. The 6-minute walk distance (6MWD) and haemodynamics were assessed at baseline and after 4 and 12 months At follow-up was 24 ± 15 months. At 4 months, significant improvements in exercise capacity and haemodynamics were observed and persisted up to 1 year. Overall survival estimates were 90 and 87% and event-free status (survival without transplantation, prostanoid initiation, or hospitalization for right heart failure) estimates were 61 and 44% at 1 and 2 years, respectively. Forty-five (44%) patients required prostanoid therapy during follow-up . The 6MWD and the right atrial pressure at baseline and the 6MWD, the increase in 6MWD, and the decrease in pulmonary resistance after 4 months of treatment were associated with long-term outcomes. Conclusion: In our series of consecutive IPAH patients treated with bosentan , improvements in exercise capacity and haemodynamics were similar to those observed in previous randomized trials. However, on the basis of local criteria, many patients required the addition of prostanoid therapy during follow-up.