After strong demand from members, the American Society of Clinical Oncology (ASCO) began, in 1992, to formulate clinical practice guidelines. Guidelines were written for the following: outcomes from cancer treatment, hematopoietic colony-stimulating factors, tumor markers for breast and colorectal cancer, surveillance of breast cancer patients, and management of non-small-cell lung cancer. Further guidelines are being drafted for management of advanced prostate cancer, antiemetics, bisphosphonates in breast cancer and myeloma, chemoprotectants, and surveillance of colorectal cancer patients. This article explores the process by which ASCO guidelines are drafted, as well problems with these guidelines. Suggestions are made for ASCO and other professional groups that anticipate framing a set of guidelines.