Small groups of adult volunteers, in sequence, were inoculated orally with inactivated purified bovine rotavirus of strain NCDV, with live NCDV purified or unpurified and with two different NCDV X human rotavirus reassortant viruses. One of five volunteers given 200 micrograms of ultravioletinactivated NCDV developed a virus-neutralizing (VN) and a binding antibody response detected by enzyme-linked immunosorbent assay (ELISA). Four of 10 volunteers given from 1 X 10(6) to 1 X 10(8) p.f.u. of live NCDV developed VN antibody, but nine of 10 responded when ELISA, HAI and radioimmuno-precipitation tests for serum antibody were also considered. Two different NCDV X human serotype 1 Wa strain virus reassortants, each containing Wa gene segment 9 and the serotype 1 neutralization phenotype, were administered orally in doses up to 10(6) p.f.u. The reassortants were relatively ineffective in eliciting a serum antibody response at the dosage level employed.