Misconceptions are common in the care of patients with inflammatory bowel disease(IBD).In this paper,we state the most commonly found misconceptions in clinical practice and deal with the use of 5-aminosalicylates and thiopurines,to review the related scientificevidence,and make appropriate recommendations.Prevention of errors needs knowledge to avoid making such errors through ignorance.However,the amount of knowledge is increasing so quickly that one new danger is an overabundance of information.IBD is a model of a very complex disease and our goal with this review is to summarize the key evidence for the most common daily clinical problems.With regard to the use of 5-aminosalicylates,the best practice may to be consider abandoning the use of these drugs in patients withsmall bowel Crohn’s disease.The combined approach with oral plus topical 5-aminosalicylates should be the first-line therapy in patients with active ulcerative colitis;once-daily treatment should be offered as a first choice regimen due to its better compliance and higher efficacy.With regard to thiopurines,they seem to be as effective in ulcerative colitis as in Crohn’s disease.Underdosing of thiopurines is a form of undertreatment.Thiopurines should probably be continued indefinitely because their withdrawal is associated with a high risk of relapse.Mercaptopurine is a safe alternative in patients with digestive intolerance or hepatotoxicity due to azathioprine.Finally,thiopurine methyltransferase(TPMT)screening cannot substitute for regular monitoring because the majority of cases of myelotoxicity are not TPMT-related. Misconceptions are common in the care of patients with inflammatory bowel disease (IBD) .In this paper, we state the most commonly found misconceptions in clinical practice and deal with the use of 5-aminosalicylates and thiopurines, to review the related scientificevidence, and make appropriate recommendations. Prevention of errors needs knowledge to prevent making errors through ignorance. However, the amount of knowledge is increasing so quickly that one new danger is an overabundance of information. IBM is a model of a very complex disease and our goal with this review is to summarize the key evidence for the most common daily clinical problems. Whith regard to the use of 5-aminosalicylates, the best practice may to be considered abandoning the use of these drugs in patients withsmall bowel Crohn’s disease. The combined approach with oral plus topical 5-aminosalicylates should be the first-line therapy in patients with active ulcerative colitis; once-daily treatment should be offered as a first choice regimen due to its better compliance and higher efficacy. Whith regard to thiopurines, they seem to be as effective in ulcerative colitis as in Crohn’s disease. Undertuction of thiopurines is a form of undertreatment. Hippurines should probably be continued indefinitely because their withdrawal is associated with a high risk of relapse.Mercaptopurine is a safe alternative in patients with digestive intolerance or hepatotoxicity due to azathioprine. F inally, thiopurine methyltransferase (TPMT) screening can not substitute for regular monitoring because the majority of cases of myelotoxicity are not TPMT-related.