Rotavirus G10P strains, which are commonly found in cattle, have frequently been associated with asymptomatic neonatal infections in India. We report the finding of G10P strains associated with severe disease in neonates in Vellore, southern India. Rotavirus strains from 43 fecal samples collected from neonates with or without gastrointestinal symptoms between 1999 and 2000 were genotyped by reverse transcription-PCR. Forty-one neonates (95%) were infected with G10P rotavirus strains, and 63% of the infections were in children who had gastrointestinal symptoms, including acute watery diarrhea. G10P strains were also seen infecting older children with dehydrating gastroenteritis in Vellore. Characterization of the genes encoding VP7, VP4, VP6, and NSP4 of these strains revealed high sequence homology with the corresponding genes of the asymptomatic neonatal strain I321, which in turn is very closely related to bovine G10P strains circulating in India. No significant differences were seen in the sequences obtained from strains infecting symptomatic neonates or children and asymptomatic neonates.