To the Editor.— Recent studies1-3have suggested that aminosalicylic acid may be as effective as sulfasalazine in the treatment of inflammatory bowel disease. These findings are promising and suggest a new avenue for drug design. Aminosalicylic acid and sulfapyridine are metabolites of sulfasalazine that are liberated in the colon by bacterial action. Most toxic effects of sulfasalazine appear related to either the parent compound, or even more likely, the sulfapyridine metabolite.4Therefore, it would be desirable to use aminosalicylic acid alone. Toxic effects would be reduced, and the drug might be used in higher doses, allowing even greater therapeutic efficacy. However, when aminosalicylic acid is administered orally, most of the drug is absorbed in the proximal intestine and eventually excreted in urine.5The drug, therefore, may not reach the colon in the manner made possible by oral administration of sulfasalazine. The studies cited previously in fact used