Although viruses are the most common cause of acute gastroenteritis (AGE) in humans, details about the causative viruses in AGE are largely unknown because many causative viruses are unable to be cultured by current culture techniques. In our study, fecal samples from 10 children under five years of age with unexplained AGE and 10 healthy children were investigated for RNA viruses using random priming (RP)-mediated sequence-independent single primer amplification (SISPA). The causative viruses in cases of cryptogenic diarrhea were then assessed for their potential diagnostic value. Of the 1,129 viral clones identified, rotavirus was most commonly associated with AGE (125 sequences, 22.4%). In contrast, bacteriophage was most common (43 sequences, 13.6%) in healthy children. The remaining 515 viral clones were unidentifiable. These findings suggest that investigation of cases or outbreaks of unexplained diarrhea using a metaviromic strategy is a new avenue for diagnosis.