Group C rotaviruses cause sporadic cases and outbreaks of acute diarrhea in children and adults in many countries but have never been identified from patients in the United States. Fecal specimens from children with diarrhea who were hospitalized in Providence, Rhode Island, were screened for group C rotaviruses if rotavirus was detected by electron microscopy but the specimens were negative for group A rotavirus by ELISA. Of 16 specimens examined, 3 were positive for group C rotavirus by ELISA using reagents specific to the Cowden strain of porcine group C rotavirus and all 16 were positive using a more sensitive assay: reverse transcriptase-polymerase chain reaction. Group C rotavirus infections occurred primarily among infants in winter in 4 of the 5 years examined and were acquired both in community and nosocomial settings. Future clinical and epidemiologic studies with group C rotavirus will require development of assays that are more sensitive and simpler to perform.