Idiopathic pulmonary arterial hypertension (IPAH) is characterized by smooth muscle cell, endothelial cell, and fibroblast hypertrophy and an increase in extracellular matrix volume in pulmonary precapillary arterioles. These features lead to a gradual increase of pulmonary vascular resistance, right-heart failure, and premature death. Bone morphogenetic protein receptor type 2 (BMPR-2) gene mutations have been identified to cause IPAH. BMPR-2 receptor mutation results in BMP signalling pathway termination and leads to disturbed growth and differentiation of pulmonary circulation cells. Transforming growth factor (TGF)-beta1 inhibits the migration and proliferation of endothelial and smooth muscle cells, and stimulates their differentiation, thus it has antiinflammatory and immunosuppressive properties, inhibiting vascular remodeling and is responsible for extracellular matrix production. The aim of this study was to analyse the profile of TGF-beta1 and the expression of its receptor (TbetaR I, TbetaR II and TbetaR III-betaglycan) genes in IPAH and in secondary forms of pulmonary arterial hypertension [Eisenmenger's syndrome (ES) patients]. Twenty-one patients with IPAH (2 men), 12 ES patients, and 10 healthy controls were enrolled in the study. QRT-PCR analysis of the transcriptive activity of TGF-beta1 and its receptor genes was performed with each patient. There were differences in receptor gene expression among the patient groups. The highest expression was observed in Eisenmenger syndrome patients (approximately 5-to 8-fold increase). There was a negative correlation between the gene expression of TGF-beta1 and that of its receptors, and a positive correlation between TbetaR II and TbetaR III in healthy controls. In IPAH patients a positive correlation between TGF-beta1 and TbetaR I was found. There was a difference in expression of TGF-beta1/receptor gene ratios and expression of receptor gene ratios between the examined groups. The differences in expression between IPAH and ES patients might suggest the role of these cytokines in IPAH pathogenesis. A disturbed proportion of expression of TGF-beta1 and receptor genes in IPAH patients might be one of the pathogenetic factors of the disease.