BACKGROUND: Clinical trial evidence in controversial areas such as complementary and alternative medicine (CAM) must be approached with an open mind. OBJECTIVE: To determine what factors may influence practitioners' interpretation of evidence from CAM trials. RESEARCH DESIGN: In a mailed survey of 2400 US CAM and conventional medicine practitioners we included 2 hypothetical factorial vignettes of positive and negative research results for CAM clinical trials. Vignettes contained randomly varied journal (Annals of Internal Medicine vs. Journal of Complementary and Alternative Medicine) and CAM treatment type (acupuncture, massage, glucosamine, meditation, and reiki). Response items also included randomly varied patient circumstances-chronic refractory symptoms and the patient requesting CAM. MEASURES: All practitioners rated the effectiveness and their willingness to recommend the therapy for a described patient. We used logistic regression to determine the independent influence of the 4 factors on respondents' effectiveness and legitimacy judgments. RESULTS: A total of 1561 practitioners responded (65%). Relative to Reiki, conventional medicine practitioners were most willing to recommend glucosamine (OR = 3.0; 95% CI [1.6-5.4]), than massage (1.9 [1.1-3.3]), acupuncture (1.3 [0.8-2.2]), and meditation (1.2 [0.7-2.0]). CAM practitioners rated acupuncture as effective more than other CAM therapies (OR = 5.8 [2.6-12.8] compared with Reiki), and were more willing to recommend acupuncture (OR = 12.3 [4.8-31.8]). When presented evidence of inefficacy, CAM practitioners were most willing to recommend acupuncture relative to other CAM therapies (OR = 15.5 [9.0-26.9]). CONCLUSIONS: Practitioners' judgments about CAM trial evidence depend on the type of treatments reported. Confirmation bias may play a role in the clinical translation of new evidence from clinical trials.