There is no correct and incorrect; it is a matter of the manual of style you're adhering to. Chicago (2.13): An em dash has no space before or after, unless yo

There is no correct and incorrect; it is a matter of the manual of style you're adhering to. Chicago (2.13): An em dash has no space before or after, unless you're doing some fancy word-replacing maneuvers with a 2-em dash. AP (p. 368): An em dash, like an ellipsis, has a space before and after, except when used to introduce items in a vertical list. http://www.apvschicago.com/2011/05/em-dashes-and-ellipses-closed-or-spaced.html http://www.apvschicago.com/2011/05/em-dashes-and-ellipses-cl... Edit: this won't be complete without mentioning Robert Bringhurst in The Elements of Typographic Style: > The em dash is the nineteenth-century standard, still prescribed in many editorial style books, but the em dash is too long for use with the best text faces. Like the oversized space between sentences, it belongs to the padded and corseted aesthetic of Victorian typography.