Purpose: Although the American Society of Clinical Onoclogy’s (ASCO) Health Services Research (HSR) committee activities have primarily focused on clinical guideline development, little is known about the value placed on these guidelines by the desired end users. ASCO members and Health Maintenance Organizations (HMOs) were surveyed on the value and implementation of ASCO guidelines. In this article, we summarize our findings. Methods: ASCO members (n = 1500) were queried about whether they had read ASCO’s first four clinical guidelines and technology assessment; whether they agreed with the recommendations; whether they used guidelines in clinical practice; and how guidelines had affected reimbursement. HMOs (n = 131) were queried on how they identify, implement, and value the first four ASCO clinical guidelines. Results: The membership survey indicated that ASCO guidelines were read more often by physicians in private healthcare settings compared with physicians in academic practices (P < .02). Disagreement rates were low for all guidelines (range, 1% to 7%). One quarter of respondents reported that the guidelines were difficult to find and difficult to apply to the practice setting, and approximately one tenth of respondents indicated that the guidelines were difficult to evaluate, interpret, or read. The HMO survey indicated that one third of HMOs reported use of ASCO guidelines, with higher rates of usage by larger HMOs and by those with higher National Committee on Quality Assurance (NCQA) ratings. Respondent HMOs valued guidelines for various purposes and used multiple methods of guideline identification and implementation. Conclusion: ASCO guidelines are generally highly supported by physicians and HMOs. Additional studies are needed to identify implementation barriers and to see whether guidelines have resulted in improvements in healthcare.