Rotavirus infections are generally recognized as a major problem in young children; however, they have also been associated with severe gastroenteritis in adults and neonates. Infections in neonates are usually asymptomatic, although the incidence of infection may be high. Adult infections also are often inapparent or mild, and thus, adults may be a reservoir of infection in pediatric wards. Diagnosis of infection is now routinely performed by enzyme immunoassay (EIA) in preference to the more cumbersome electron microscopy (EM). A commercial polyclonal EIA test, Rotazyme (Abbott Laboratories, North Chicago, Ill.), has been widely used for this purpose. The efficacy of this assay in adults has not been described, and reports of false-positive reactions in samples from neonates have resulted in recommendations that Rotazyme not be used with neonatal stool specimens. False-positive results in neonates have also been reported for other rotaviral EIA tests based on polyclonal sera.