Observational methods are often used to study alcohol withdrawal syndrome. Observational cohorts and case-control studies are useful in research on prognosis and in situations where ethical concerns might prevent the use of clinical trial designs. In addition, case-control studies are appropriate for studying the rare but serious complications of alcohol withdrawal syndrome. Despite their appeal and suitability, these methods are subject to a number of biases that can render their results suspect. Susceptibility, diagnostic suspicion, and exposure suspicion bias are among the important biases to consider in observational studies on alcohol withdrawal syndrome. Strategies for reducing these biases include the creation of inception cohorts, the use of operational definitions, and blinding. Increased attention to these strategies should help clinicians and researchers improve the practice of caring for patients with alcohol withdrawal syndrome.