Introduction: Pulmonary arterial hypertension (PAH) is a multifactorial disease associated with high morbidity and mortality. However, the diagnosis and therapeutics strategies used in most of the Argentinean regions are poorly known. The advanced functional class (FC) is an indicator of poor prognosis and one of the therapeutic goals. Aims: 1-To determine the impact of advanced FC in patients with PAH on established markers of poor prognosis, such as clinical, biomarker, hemodynamic, and echocardiographic parameter 2-To compare treatment strategies between an advanced and non advanced FC Method: Between July 2014 and May 2015, 170 patients with confirmed PAH were prospectively included in a multicenter, collaborative, observational registry by 60 investigators from 20 provinces in Argentina. Inclusion criteria were as follows: 1-patients over three months of age; 2-mean pulmonary arterial pressure (mPAP) at rest ≥ 25 mmHg by right heart catheterization (RHC) and 3 - clinical stability in the absence of hospitalization in last month. WHO FC III or IV at diagnosis was defined as advanced (AFC) whereas WHO FC I or II were considered as non advanced (NAFC) Results: Mean age was 50.5 years (SD 18) and 79% were female. According with the Nice classification, the distribution was: idiopathic 51.6%, inherited 1,6%, drugs 2.4%, connective tissue disease 15.3%, portal hypertension 1.6% and congenital heart disease 27.4%. WHO FC at initial diagnosis was: I: 3%; II: 27%; III: 45% and IV: 25% and during follow-up was: I: 19%, II 54%, III 21% and IV 6% (p < 0.001). AFC at initial diagnosis was 70% and during follow up 27% (p < 0.001). Clinical manifestations in AFC compared with NAFC was: syncope 11 vs 13% (NS); heart failure 30 vs 4% (p < 0.001); BNP 372 vs 158 pg/ml (0.02), NT-proBNP 1595 vs 668 pg/ml (0.012), TAPSE 17.2 vs 19.3 mm (0.032), pericardial effusion 18 vs 10% (p = 0.020); 6MWT 367 vs 373 (NS); CI 2.6 vs 2.8 (NS); RAP 12.3 vs 10 mm Hg (NS);. PAH targeted drugs in AFC was = None in 26.7%, Monotherapy in 31.4% and Combined therapy in 41.9%. Conclusion: In our registry of PAH, we observed a high percentage of patients with AFC (70%) at initial diagnosis and a significant decrease during follow-up (27%). Advanced FC at initial diagnosis was significantly associated with other variables of poor prognosis. These findings emphasize the need for strategies for early detection and therapy.