There are multiple practice guidelines published pertaining to diabetes care. Experts have formulated methodologic standards of guideline formulation. The objective was to determine whether practice guidelines pertaining to diabetes and published in peerreviewed publications and the Internet adhered to established methodologic standards of guideline development. We identified all guidelines pertaining to diabetes care published between 1980 and 2000 using a computerized search of Medline, the Practice Guidelines Clearinghouse, the Institute for Clinical Systems Improvement Web site, and a global Internet search engine. We used a previously validated 25-item assessment tool to determine guideline adherence to methodologic standards in three categories: guideline development and format, identification and summary of evidence, and formulation of recommendations. We conducted a multivariable regression analysis to determine the influence of guideline author, publishing medium, year of publication, and guideline length on adherence to methodologic standards of guideline development. We evaluated 43 guidelines: 33% published on the Internet, 66% in peer-reviewed journals; 51% published by organizations and 49% by individual experts. Of a maximum of 25 methodologic standards, the number of standards adhered by a guideline was 9 (range, 2 to 19). Mean proportion (SD) of guidelines that adhered to methodologic standards on guideline development and format was 48% (28); on identification and summary of evidence, 21% (22); and on the formulation of recommendations, 36% (27). Longer guidelines had greater adherence to methodologic standards (P < 0.0001). Guidelines pertaining to diabetes care published on the Internet and in peer-reviewed publications do not meet most methodologic standards of guideline development.