THREE trials were conducted in Nagoya, Japan, testing the safety, antigenicity, contagiousness, and transplacental passage of RA27/3. Trial 1 was performed with children in a closed orphanage and with nurses attached to two hospitals in Nagoya. Most of the 43 seronegative subjects in the orphanage were between 1 and 2 years of age, with a range from 8 to 35 months. The other subjects were 16 adult women whose ages ranged from 19 to 25 years. In the orphanage, seven rubella susceptible uninoculated children were placed in two rooms where there was ample opportunity for close contact with inoculated children, while playing and napping together. In the other two trials, the subjects were selected from nursing students at another hospital; 105 were seropositive, and 21 were seronegative. The total number inoculated in the three trials, therefore, included 80 seronegative and 111 seropositive subjects. Of the seronegative subjects, 37 were