Background: The Internet is a popular medium for disseminating information relevant to oncology practitioners. Despite the widespread use of web-based guidelines and protocols, the quality of these resources has not been evaluated. This study addresses this gap. Methods: The Appraisal of Guidelines for Research and Evaluation (AGREE-II) instrument was used to assess the quality of breast and sarcoma guidelines and protocols according to six independent domains. The oncology resources were selected from eight websites developed for healthcare settings in North America, the United Kingdom, Europe, and Australia. Results: Mean quality scores across domains were highly variable for both guidelines (29-73%) and protocols (31-71%). Guidelines scored highly in terms of articulating their Scope and Purpose (72.6±11.2%) but poorly with respect to Applicability in clinical practice (29.0±17.3%). Protocols scored highly on Clarity of Presentation (70.6±17.6%) but poorly in terms of the processes used to synthesise underlying evidence, develop, and update recommendations (30.8±20.0%). Conclusion: Our evaluation provides a quick reference tool for clinicians about the strengths and limitations of oncology resources across several major websites. Further, it supports resource developers in terms of where to direct efforts to enhance guideline and protocol development processes or the communication of these processes to end-users. © 2011 Cancer Research UK All rights reserved.