Dehydration secondary to acute gastroenteritis is a commonly encountered condition among patients presenting to physicians' offices and hospital EDs. Treatment options consist of oral rehydration therapy (ORT), intravenous rehydration therapy (IVRT) and subcutaneous rehydration therapy (SCRT). Although most patients with dehydration can be effectively treated in an outpatient setting, hospitalization is frequently warranted, with estimated annual inpatient costs for dehydration therapy exceeding $US1 billion in the US in 1999 for elderly patients alone. Although most treatment guidelines recommend ORT as first-line treatment for mild to moderate dehydration, IVRT remains the predominant route of administration for rehydration fluids in the acute care setting in the US. To evaluate the current state of the literature examining costs associated with dehydration therapy, a systematic review of articles published on MEDLINE from 2000 to 2009 was conducted. A total of 20 reports containing pharmacoeconomic data on rehydration therapy were evaluated. Findings suggest that ORT and SCRT may be less costly than IVRT in the treatment of mild to moderate dehydration; however, variability in cost parameters examined or data collection methods described in the literature precluded a comprehensive comparative cost-effectiveness analysis of treatment options.