The aim of this study was to investigate whether, the vaccine Priorix causes less immediate injection pain than MMR-II in vaccination of infants aged 18-24 months who were offered vaccine against measles, mumps and rubella. The infants were randomised into one of the two vaccine groups (Priorix/MMR-II in a double-blind study. One observer assessed pain, using CHEOPS (Children's Hospital Eastern Ontario Pain scale), and the parent used the Visual Analogue Pain scale (VAS). Pain assessment was made in 295 infants. Mean age was 19.08 months. Mean VAS value was 2.3/5.2 for Priorix and MMR-II, respectively (p<0.001). Mean CHEOPS value was 1.9/6.1 for Priorix and MMR-II, respectively (p<0.001). The study shows that Priorix gives less immediate injection pain than MMR-II.