Depression, obesity, diabetes mellitus, and the metabolic syndrome are conditions commonly treated in primary care. The prevalence of each condition separately does not explain the frequency of their co-occurrence. Depression may lead to or exacerbate these endocrine and metabolic conditions. Conversely, these medical conditions may lead to or exacerbate depression. Psychotropic drugs that treat depression may increase appetite with resultant weight gain. Rarely, such agents may be associated with weight loss. We review the potential for psychotropic drugs to alter body weight and provide a table as a guide to drug selection. Unless circumstances dictate otherwise, clinicians should select psychotropic drugs least likely to induce weight gain when treating depressed patients with obesity, diabetes mellitus, or the metabolic syndrome. Even drugs generally thought to be "weight neutral" may occasionally be associated with weight gain. Thus, alerting patients to this potential and due diligence form the cornerstone of weight management in the depressed patient.