About 4 yrs ago, I never really understood why I would be able to see pro's inner side of string (the side that just hit the ball) right after they hit the serve. I simply thought that they snap their wrist so much it happens. True to certain extent. But I could mainly see THAT side of string because of their standing in angle. (Think of your stance, you don't stand facing straigt to the other side) Then I heard the term "pronation", started wondering what it really meant, if it was really different from wrist snap, and if I was "pronating". It took me a really long time to figure it out (thanks to my slow brain). First, let's define pronation. It's a very simple action of your hand (palm) turning inside out. Notice, you CANNOT pronate your hand without pronating your forearm. So there really is no such thing as "wrist pronation" or "forearm pronation". There is "wrist and forearm pronation" When you are in backscratch position, buttcap is pointing towards sky. As you swing UP for the ball, your racket face will start to open up. This opening is due to pronation. You can still pronate even though you don't go up for the ball AS MUCH, but won't be a great serve. Second, Pronation in different serves. The rate of open is prett early for the flat serve. You cannot possibly hit flat serve with closed racket face. I know flat serve has SOME spin. But the whole purpose of flat serve is to hit it "with less spin", and "more penetrating". On slice serve, pronation happens much late. If you think logically, you want to hit the ball at 1,2 o'clock. So your racket face has to be a bit more closed than flat serve. Usually the pronation on slice serve happens after contact. BUT some people DO hit without pronation on slice serve. They simply carve around the ball. I have done it, I have seen people doing it. I am not sure which is more effective. Kick serve. Pronation happens in different direction. Your swing path is pretty much sideways, and there really is not much forward swing to it. You cannot possibly hit a good kick serve if you don't swing up. Swing path is such that, when viewed from behind the server, the tip of the racket will draw an arch. I think pronation happens earliest in kick serve. Follow through of kick serve can be deceiving. Agassi doesn't look like he pronates on kick serve, if you look at his follow through. And you see Sampras, he obviously pronates. I think it's just different way of follow throughing. Some people say that hitting at 1:00 on the ball will give you kick. I agree, I have done it, and I know a guy who does it as well. I don't know how much improvement you can make with that motion. But some of my best kick serve came from pronating. Pronating and wrist snap. These are two separate motion, at least in my opinion. People hitting slice/kick serve without pronation are still using their wrist, intentionally or unintentionally. Some people would argue that "carving around action" on slice serve is still a wrist snap. Some people will argue that wrist doesn't SNAP from reading tennisone article a long time ago. But I am sure you have seen pics of pro's snapped wrist after serve. But when you are pronating, i think you serve becomes "heavier" There are mutilple actions leading upto "wrist snap". I think main factor is hip strectch. Entire body is like a bent pole. And if you have something loose attached on the top, it's going to "SNAP forward/downward" after you let the bent pole go. B Bill can probably explain this much better. So my conclusion is that you can still hit serve without pronation NOT on flat serve. And pronation is seperate motion from wrist snap. I think it's sometimes too difficult to pay too much attention to too little things. Instead of forcing pronation, concetrate on hitting the ball squre with loose arm and grip while you keep your head up. If you keep your grip loose, and have a decent motion, then wrist snap will happen naturally. I once asked Taylor Dent (atptour.com), about wrist snap and pronation. His reply was that he doesn't like to get into too much technical. And he thinks that loose arm and timing are the most important part.