BACKGROUND AND AIMS: Severe tricuspid regurgitation (TR) is associated with increased mortality and hospitalizations for heart failure (HF). Aetiologies of TR include: secondary (atrial or ventricular), primary and cardiac implantable electronic device (CIED)-related. The aim of the study was to assess the prevalence of different TR aetiologies, as well as characteristics and treatment of patients with severe TR in a real-life setting. METHODS: This was a prospective, observational study of patients with severe TR, conducted in 18 cardiology centres. Consecutive adult patients with severe TR were included, regardless of the presence of TR symptoms and the cause of hospital admission. RESULTS: A total of 1295 patients with severe TR were enrolled (median age 76 years, 53% women). The most common reason for admission was HF decompensation (40%). Single TR aetiology was identified in 79% patients. The most frequent overlap between aetiologies included secondary ventricular and atrial TR, and was found in 11% of patients. The most common TR aetiology was secondary atrial (37%), followed by secondary ventricular (25%). Primary and CIED-related TR accounted for 10% and 15%, respectively. In 2.4% TR aetiology was not determined. Patients with secondary atrial and CIED-related TR were the oldest (79 and 78 years, respectively), and those with primary TR the youngest (68 years). Patients with CIED-related and secondary ventricular TR were more often hospitalized for HF decompensation, had more advanced HF symptoms, worse left- and right-ventricular function, worse kidney and liver function, and higher in-hospital mortality. Only 40% of patients underwent evaluation by the Heart Team and 21% were qualified for TR interventions. CONCLUSIONS: In real life, unequivocal identification of TR aetiology remains challenging. Secondary atrial TR is the most common aetiology. There are significant differences in characteristics and outcomes depending on TR aetiology. Too few patients with severe TR undergo evaluation by the Heart Team.