Despite the emergence of new biological therapies that aim for mucosal healing as a new therapeutic target, the importance of 5-ASA formulations in the standard treatment for inflammatory bowel diseases, particularly ulcerative colitis, remains unchanged. With a growing number of patients suffering from inflammatory bowel diseases in Japan, general physicians are also increasingly prescribing 5-ASA formulations. In order to obtain the maximum efficacy of 5-ASA formulations when treating inflammatory bowel diseases, it is essential that the dosage and administration are appropriate.