I have studied TKD and have taught TSD and I agree with TangSooGuy. The main difference between the two is the primary focus of the art. I say this with all due respect to the TKD guys out there, but TKD does tend to be more sports oriented than TSD. But then again, I did my TSD training in Korea which is a totally different animal than training here in the U.S.. TSD has all of the same kicks as TKD, but we focused more on hand techniques, throws and even ground fighting. IMO, I felt like TSD provided more "real world" training than TKD did.