Sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP) specific phosphodiesterase-5 inhibitor, has shown promising results as a novel oral monotherapy in the treatment of pulmonary arterial hypertension (PAH). We conducted a cross-sectional survey of 19 consecutive PAH patients, aged 16-75 years, with WHO functional class II or worse over 3 months of oral sildenafil. Improvement in exercise capacity was achieved in 15/19 (79%) patients. 6-minute walk test distance increased from 299+/-118 m to 360+/-127 m, p=0.016, and WHO functional class decreased significantly. Both PASP and CI showed a non-significant trend toward improvement. Patients also reported significant improvement in physical (p=0.002) and social (p<0.001) functioning, and general health (p=0.01) of Rand SF-36 questionnaire. There was improvement in domains of role limitation due to physical health (p=0.16), emotion (p=0.14), and energy level (p=0.4). Our study suggests that oral sildenafil monotherapy is effective in improving exercise capacity and health-related quality of life amongst PAH patients. (C) 2006 Elsevier Ireland Ltd. All rights reserved.