The American Society of Clinical Oncology (ASCO) published its first clinical practice guideline, which focused on the use of hematopoietic colony-stimulating factors, in 1994. Since then, ASCO has published 24 additional guidelines or technology assessments on a range of topics and is developing 11 additional guidelines. Guidelines are among ASCO's most valued products, according to membership surveys and data from the JCO.org Web site. However, the same data from ASCO members have highlighted a number of limitations to the guideline program. These relate to the timelines of guideline updates, difficulties locating guidelines and related products, and challenges to implementing ASCO guidelines in everyday clinical practice. This article outlines the concrete steps that the ASCO Health Services Committee (HSC) is taking to address these limitations, including the institution of a more aggressive guideline updating schedule, a transition from narrative to systematic literature reviews to support the practice recommendations, a new Board of Directors-approved policy to permit endorsement of other groups' guidelines, and a robust Clinical Tools and Resources program that offers a range of guideline dissemination and implementation aids. Additional work is underway to establish stronger and deeper collaborations with practicing oncologists to expand their role in the review, field testing, and implementation of guideline clinical tools and resources. Finally, the HSC is discussing evaluation of the guidelines program to maximize the impact of ASCO clinical practice guidelines on clinical decision making and, ultimately, the quality of cancer care.