Using the course-of-action theory (Theureau, 1992), which is a situated cognition approach, this study analyzed the knowledge used by three expert table tennis players in the course of official competitions. Matches were videotaped during international meets and then supplemented a posteriori by prompted verbalization data. The verbal protocols were coded according to the course-of-action theory. The knowledge used during the matches was categorized by content and form. The analysis showed that the players' knowledge was about their game, their opponent's game, and the game in general independent of each player's particularities. This knowledge was expressed in the form of types and general principles. The results point out the diversity of knowledge used in the course of a match. Knowledge activation engages players in activities of reproducing effective actions, exploring the opponent's game, and concealment.