Despite its popularity and competitive status there have been only few scientific studies that have examined Futsal in professional players. Consequently the aim of this study was to examine the physiological responses and activity pattern to Futsal simulated game-play in professional players. Eight full-time professional outfield Futsal players volunteered for this study: age 22.4 (95% CI 18.8-25.3) years, body mass 75.4 (60-91) kg, height 1.77 (1.59-1.95) m and VO2max 64.8 (53.8-75.8) ml kg(-1) min(-1). Physiological measurements were assessed during highly competitive training games (4x10-min quarters) and consisted of game VO2, game blood-lactate concentration ([la](b)) and game heart rates (HRs). Game activities were assessed using a computerised video-analysis system. During simulated game-play players attained 75% (59-92) and 90% (84-96) of VO2max and HR(max), respectively. Mean game VO2 was 48.6 (40.1-57.1) ml kg(-1) min(-1). Peak game VO2 and HRs were 99% (88-109) and 98% [90-106] of laboratory maximal values, respectively. Players spent 46 and 52% of the playing time at exercise intensities higher than 80 and 90% of VO2max and HR(max), respectively. Mean [la](b) was 5.3 (1.1-10.4) mmol l(-1). Players covered 121 (105-137) m min(-1) and 5% (1-11) and 12% (3.8-19.5) of playing time spent performing sprinting and high-intensity running, respectively. On average players performed a sprint every approximately 79 s during play. These results show that Futsal played at professional level is a high-intensity exercise heavily taxing the aerobic and anaerobic pathways.