19 sportsmen from 17 to 55 years old, all right-handed and national second seeded players took part in this study. The electro encephalogramme was collected by the ambulatory Holter E.E.G. method on an equipment MS 40 Micromed Brian-Spin. The layind of the electrodes was done tothe international 10-20 reference Wilson type system. Each subject played a tennis match witch the order to win the point hitting the ball no more than 3 times. That order expressing, in the mind of the coaches a pattern of offensive aggressiveness. Meanwhile each subject was recorded with the E.E.G. acquisition. This, we could separate the points they won and the points they lost and then study the encephalographical information. A second succession of measure was realised so as to know the artefacts linked to measure in actual situation and on the other hand to quantify the level of activation linked to the motory activity started by sport gesture. For each lost or won point the analysis of the E.E.G. frequencies and thir amplitude at the level of the left hemisphere as well as the right hemisphere was visually studied. The statistic analysis was about the Chi 2 test on the standard variations and the average of the frequencies. A complementary study in a labotary and and homogeneousness of the population are necessary to quantify more precisely the E.E.G. modification and their link to the performance. However aggressiveness appears as a psychological component we can not dissociate from the performance in sport.