Evidence-based guidelines are regarded as therapeutic standards for many medical interventions. However, implementation of such recommendations seems to be rather difficult. An international antiemetic guideline for the treatment of patients undergoing chemotherapy was issued by the Multinational Association of Supportive Care in Cancer in 1997 and has been in use ever since. However, for many reasons, the guideline has not been followed completely, despite the fact that if antiemetics are used in accordance with guidelines, efficacy is similar to that achieved in randomised controlled trials. Structural dificulties, patients characteristics, and other barriers, such as the individual acceptance of guidelines and education of physicians and nurses, could be crucial factors for successful implementation. Thus, better adherence to antiemetic guidelines can only be achieved through a complex and long-term process, consisting of efficient education, training, and monitoring of all individuals involved.