To compare measles seroconversion rates (development of antibodies) at 13 months of age in HIV-infected and uninfected children on one of two immunization schedules: attenuated measles/mumps/rubella virus (M-M-R II) vaccine at 12 months versus attenuated measles vaccine (Attenuvax) at 6 months plus M-M-R II vaccine at 12 months.