Make Your Case, And Don’t Worry About the Other Guy

What’s your advice on asking for a raise in a delicate workplace situation? I’ve been with my company almost six years, and I make the same money as one of my co-workers, who has been with the company for an equal amount of time and holds the same title. I have no problem, all things being equal, but in my mind they’re not equal. During our tenure with the company, I have consistently taken on more responsibility—asked for it, even—and produced bigger and better results than he has. All things considered, at this point I feel I have the right to complain about the situation, because I think I should be making more money than he does.