Semi-formal wear for men includes dark suits, dress shirts and ties. Semi-formal wear is just one step down from black tie optional wear, and some men prefer to dress more toward that style than the dressy causal style.
Dark business suits are appropriate for semi-formal events. Some men choose to wear tuxedos at semi-formal events, such as evening weddings or galas. Tuxedos are acceptable, though are more commonly associated with white tie, black tie and black tie optional styles. If a suit is worn, a matching vest can also be worn.
Dress shirts can be white, but a conservative color is appropriate as well. It is imperative that the colored shirt match the dark business suit. The shirt, regardless of color, should be pressed and crisp.
A dark tie or bow tie is expected in semi-formal dress. As with shirts, a conservatively colored tie can be worn, but not a wildly patterned or ostentatious tie. A dark tie looks more formal than a colored tie, so solid and dark work better if the event is more formal.
Leather dress shoes and a leather belt are required for semi-formal wear. Dark colors, preferably those that match the suit, are best. Dark dress socks are also a must.