Objective: To evaluate health professionals’agreement with components of published diagnosticcriteria for fetal alcohol spectrum disorders (FASD) inorder to guide the development of standard diagnosticguidelines for Australia.Design: A modified Delphi process was used toassess agreement among health professionals withexpertise or experience in FASD screening ordiagnosis. An online survey, which included 36 Likertstatements on diagnostic methods, was administeredover two survey rounds. For fetal alcohol syndrome(FAS), health professionals were presented withconcepts from the Institute of Medicine (IOM),University of Washington (UW), Centers for DiseaseControl (CDC), revised IOM and Canadian diagnosticcriteria. For partial FAS (PFAS), alcohol-relatedneurodevelopmental disorder (ARND), and alcoholrelatedbirth defects (ARBD), concepts based on theIOM and the Canadian diagnostic criteria werecompared.Setting/participants: 130 Australian and 9international health professionals.Results: Of 139 health professionals invited tocomplete the survey, 103 (74.1%) responded, and74 (53.2%) completed one or more questions ondiagnostic criteria. We found consensus agreementamong participants on the diagnostic criteria for FAS,with the UW criteria most commonly endorsed whencompared with all other published criteria for FAS.When health professionals were presented withconcepts based on the Canadian and IOM diagnosticcriteria, we found consensus agreement but no clearpreference for either the Canadian or IOM criteria forthe diagnosis of PFAS, and no consensus agreementon diagnostic criteria for ARND. We also found noconsensus on the IOM diagnostic criteria for ARBD.