All 20 children who received Enders'' original measles vaccine and human immune globulin, retained measles antibody for 15 yr with essentially no decline in antibody titer. All but 1 of 24 children who received Enders'' original measles vaccine and all of 33 children who received more attenuated measles virus vaccine (Moraten line, Attenuvax) retained their antibody for 8 yr, the longest time period tested. The problems with efficacy of measles virus vaccine are apparently more related to handling and administration of the vaccine itself than with the attributes of the vaccine.