Of 121 children vaccinated for measles in Zaïre, antibody studies revealed that 69% sero-converted. These included 53% of children vaccinated by two shots of a dermojet (0.2 ml i.d.) and 80% of children vaccinated by 0.5 ml subcutaneously. Whilst a dermojet gives less good results, a decision on its use needs to be made in each individual situation, particularly taking into account the quantity of vaccine available for the number of children presenting for vaccination. At six months of age 59% of children sero-converted. This did not reach 100% until 16 months of age. In view of the young age of children getting measles in Zaïre, there would seem to be value in vaccinating at six months, but this needs to be repeated at 16 months if full cover is required.