5-Aminosalicylic acid is an anti inflammatory drug used to treat inflammation of the digestive tract (Crohn's disease) and mild to moderate ulcerative-colitis. 5-Aminosalicylic acid is a bowel-specific aminosalicylate drug. It was developed an amperometric biosensor for determination of 5-aminosalicylic acid concentration and measurement technique is based on substrate-competition. The biosensor is more suitable especially for routine 5-aminosalicylic acid analysis because it is simple to construct and sensitive, specific and does not require any expensive apparatus. This enzyme based biosensor was made with a couple of enzymes which uses the same substrate. ne electrode was developed to determine measurement conditions and also characterized.