Background: In comparison to the amount of literature that has examined the match demands of football refereeing, there has been little attempt to assess the impact of high-intensity training. Purpose: The main goals were to get a better understanding of the long-term effect of specific intermittent training. Study Design: The authors examined the cardiovascular strain of specific high-intensity training sessions and also their impact on referees' fitness levels. Methods: To examine the physical workload during intensive intermittent training sessions, heart rates were recorded and analyzed relative to the referees' maximum heart rate (HRmax). To assess the referees' fitness levels, the Yo-Yo intermittent recovery test was used. Results: Both the pitch- and track-training sessions were successful in imposing an appropriate high intensity load on the referees, at 86.4 ± 2.9% and 88.2 ± 2.4% HRmax, respectively. Following 16 months of intermittent high-intensity training, referees improved their performance on the Yo-Yo intermittent recovery test by 46.5%, to a level that is comparable with professional players. Conclusions: As match officials are subjected to a high physical load during matches, they should follow structured weekly training plans that have an emphasis on intensive, intermittent training sessions.