PURPOSE: To examine the improvement in swimming (3.8 km), cycling (180 km), running (42.2 km), and overall performances at the Hawaii Ironman Triathlon of elite males and females between 1981 and 2007. METHODS: Trends across years, gender differences in performance times in the three disciplines, and overall winning times of the top 10 males and females were analyzed. RESULTS: Overall performance time in the ironman decreased rapidly from 1981 but has remained stable since the late 1980s. From 1988 to 2007, linear regression analysis showed that change in swimming, cycling, running, and total performance for both males and females was less than 1.4% per decade, except for females' running time, which decreased by 3.8% per decade. Since 1988, the mean (SD) gender differences in time for swimming, cycling, running, and total event were 9.8% (2.9), 12.7% (2.0), 13.3% (3.1), and 12.6% (1.3), respectively. CONCLUSIONS: After an initial phase of rapid improvement of performances during the 1980s, there was a relative plateau, but at least in running and cycling, there were small improvements. Over the last two decades, gender difference in swimming remained stable while it slightly increased in cycling and decreased in running. The gender difference in ironman total performance is unlikely to change in the future.