There is a chorus of complaints that many professional tennis players who grunt when striking the ball gain an unfair advantage because the sound of the grunt distracts their opponent. However, scientific investigations of human attention and performance, specifically with regard to sound-vision interactions, would seem to predict that a grunting sound should help because it will draw attention to the visual event of a ball being struck. We tested the argument that a grunt has a negative impact by requiring participants to view videos of a professional hitting a ball to either side of a tennis court with or without a grunt. The task was to respond as quickly as possible to the balls direction. Grunting interfered with performance making responses slower and less accurate. The competitive advantage afforded to the grunting player is potentially profound. The findings will be discussed in relation to current theory on multisensory integration.