No, as long as you strike the ball before you touch or go over the line. The server steps on or over the endline while serving. (Foot Fault) RULE 11: Foot Fault The server shall, throughout delivery of the service, up to the moment of impact of paddle on ball (a) not change position by walking or running; (b) not touch, with either foot, any area other than that behind the baseline within the imaginary extension of the center mark and the sideline. Note: The server shall not by the following movements of his/her feet be deemed to “change position by walking or running”: (a) slight movements of the feet that do not materially affect the location originally taken by the server; (b) an unrestricted movement of one foot, so long as the other foot maintains continuously its original contact with the deck; (c) leaving the deck with both feet. In a match not being officiated, the server’s opponents may call foot faults. The first call of a foot fault on each server shall be a let. After this grace fault, it is loss of point. Under tournament conditions, if there is an umpire or linesmen, they assume the responsibility for calling all foot faults. At any time in any round of a tournament match, any player is entitled to request a foot fault judge and/or linesmen. http://www.ptmonline.com/about_rules.asp