Purpose - To describe heart rate responses of referees during a major international basketball championship. Methods - Heart rate (HR) data was collected from 26 international referees officiating 48 matches (95 matches ‘worth’ of data) at the 2011 Eurobasket Championship. HR was subsequently normalised to percentage of theoretical maximum, and used to calculate time spent in different exercise intensity zones (Light, moderate, heavy, very heavy) across successive phases of the tournament and successive quarters (Q) of matches. Results - Mean HR was 81.89±13.4% of theoretical maximum during match play, and there were no significant differences in HR recorded during different phases of the championship. However, relative HR progressively decreased with each quarter of the matches (Q1; 91.43±7.6%, Q2; 90.51±7.1%, Q3; 88.23±7.3%, Q4; 88.21±7.5% HRmax). This decrease in %HRmax recorded relative to Q1 reached statistical significance (P<0.05) in Q3 and Q4. Although percentage of total match time spent in ‘hard’ and ‘light’ exercise intensity categories remained similar across quarters of matches, there was a reduction in time spent in ‘very hard’ activity from 10.93±16.08% in Q1 to 5.73±10.36% in Q3 and 5.55±10.74% in Q4 (both P<0.05). This reduction in ‘very hard’ activity was accompanied by an increase in ‘moderate’ intensity activity from 15.06±14.29% in Q1 to 23.37±17.12% in Q3 and 24.35±20.31% in Q4 (both P<0.01). Conclusions - The data suggests that international basketball referees are unable to maintain initial exercise intensity for four successive quarters of championship play. This is in contrast to available data suggesting elite players are able to maintain or increase exercise intensity as matches progress. This has implications for the physical conditioning requirements of international level match officials.