Classical migraine involves unilateral headache, visual disturbance, nausea, and vomiting, sometimes together with abdominal pain. These are the end point of a number of different factors in a predisposed individual. One factor, although not usually the most important, is food intolerance. Since there are many other factors which may precipitate an attack and since in some migraine sufferers food does not appear to be a factor, the response to food avoidance is very variable and often disappointing. In some individuals where food plays a role, other triggers are also present, so that food avoidance does not stop attacks altogether.