Participation in ultra-endurance performance is of increasing popularity. We analyzed the historic development of the ultra-triathlon scene from 1985 to 2011 focusing on a) worldwide distribution of competition, b) participation, c) gender, and d) athlete nationality. We examined the participation trends of 3,579 athletes, involving 3,297 men (92.1%) and 300 women (7.9%), using linear regression analyses. Between 1985 and 2011, a total of 96 Double Iron ultra-triathlons (7.6km swimming, 360km cycling, and 84.4km running), 51 Triple Iron ultra-triathlons (11.6km swimming, 540km cycling, and 126.6km running), five Quadruple Iron ultra-triathlons (15.2km swimming, 720km cycling, and 168.8km running), five Quintuple Iron ultra-triathlons (19km swimming, 900km cycling, and 211km running), 11 Deca Iron ultra-triathlons (38km swimming, 1,800km cycling, and 422km running), and two Double Deca Iron ultra-triathlons (76km swimming, 3,600km cycling, and 844km running) were held. In total, 56.7% of the races were in Europe, 37.4% in North America, 5.3% in South America, and less than 1% in Asia. Europeans comprised 80% of the athletes. The number of male participants in Double (r2 = .56; P < .001) and Triple Iron ultra-triathlon (r2 = .47; P < .001) and the number of female participants in Double Iron ultra-triathlon (r2 = .66; P < .001) increased significantly. Less than 8% of the athletes total participated in an ultra-triathlon longer than a Triple Iron ultra-triathlon. Europeans won by far the most competitions in every distance. In conclusion, ultra-triathlon popularity is mainly limited to a) European and North American men and b) Double and Triple Iron ultra-triathlons. Future studies need to investigate the motivation of these ultra-endurance athletes to compete in these extreme races.