Black tie is the most formal tier of the wedding guest dress code. This style of wedding requires that gentlemen wear black tuxedos or formal dinner jackets (not suits) with black bow ties, formal dress shirts (traditionally pleated), and black dress shoes. Women should wear long formal evening gowns with dress shoes.
Black tie optional weddings require a formal style of dress, but not necessarily as formal as black tie. Gentlemen could opt to wear a nice suit and tie instead of a tux, for example, and ladies could wear less formal cocktail attire. But in general, we suggest dressing up versus dressing down for black tie optional events. Why not dress to impress for such a special day?