Studies are necessary to monitor the effects, if any, of these recommended changes in IE prophylaxis. The incidence of IE could change or stay the same. Because the incidence of IE is low, small changes in incidence may take years to detect. Accordingly, we urge that such studies be designed and insti- tuted promptly so that any change in incidence may be detected sooner rather than later. Subsequent revisions of the AHA guidelines on the preven-tion of IE will be based on the results of these studies and other published data. Acknowledgments The writing group thanks the following international experts on infec- tive endocarditis for their valuable comments: Drs Christa Gohlke- Ba rwolf, Roger Hall, Jae-Hoon Song, Catherine Kilmartin, Catherine Leport, Jose M. Miro , Christoph Naber, Graham Roberts, and Jan T.M. van der Meer. The writing group also thanks Dr George Meyer for his helpful comments regarding gastroenterology. Finally, the writing group would like to thank Lori Hinrichs for her superb assistance with the preparation of this manuscript. 