We evaluated safety and immunogenicity of two orally administered human rotavirus vaccine candidates 116E and I321. Ninety healthy infants aged 8 weeks received a single dose of 116E (10(5)FFu (florescence focus units)), I321 (10(5)FFu) or placebo. There were no significant differences in the number of adverse events. Fever was reported by 6/30, 1/30 and 5/30 in the 116E, I321 and placebo groups; the corresponding figures for diarrhoea were 5/30, 8/29 and 3/30. Serum IgA seroconversion rates were 73%, 39% and 20% in the 116E, I321 and placebo groups, respectively. Vaccine virus was shed on days 3, 7 or 28 in 11/30 infants of the 116E and none in the other two groups. The 116E strain is attenuated, clinically safe and highly immunogenic with a single dose.