This proposed study will be based upon the randomised, placebo-controlled National Cancer Institute sponsored study in which three groups of FAP patients were assigned to one of two doses of celecoxib (a COX-2 inhibitor) or placebo. The results showed a reduction in the polyp burden of the group taking the higher (400mg twice daily (bd)) dose. However, there is evidence to suggest that COX-2 inhibitors carry significant potential for side-effects. Adopting a similar design, EPA will be substituted for celecoxib in this randomised, placebo-controlled trial, comparing 2g EPA to placebo, with reduction in polyp burden as the primary objective.