I ordered this dress in a Medium and it fit me perfectly. It is a little snug in the bust but since I am small busted, that is no problem for me. It is definitely fitted, so if you are looking for a looser fitting dress, this one is not for you. I found the fit very flattering, not too tight or too loose. I am 5'4" and I did have to hem it, that's the only reason for the 4 stars instead of 5.
i have 3 other fila tennis dresses that i absolutely love! all 3 are size small and fit perfectly. i like the fact that they are a relaxed fit, not too big but not clingy. i ordered this dress in a small and the built in bra area was so tight i barely got it on or off so i ordered the medium. it wasn't much larger in the problem area but it was too large in the bust area under the arms. and it was still difficult to remove - i thought i pulled a muscle! i hope fila hasn't adjusted it's sizing because i hope to purchase more dresses in the future.