100% Polyester. I am 5’9 wearing a size medium. I have a 35” bust and the elastic on the small sat right under my busy making it look like a shelf. If you aren’t busty no need to size up. Best thing about this dress is that it also has a tie in the neck if you do have to size up! Small (0-4) Medium (4-8) Large (8-12) Size small length appx. 52" Bust 17" My stats are bust 36”. Waist 27”. Hips 36”.