An open, randomized multi-center trial, involving 700 infants, was conducted in order to compare a new measles mumps rubella (MMR) vaccine, SB MMR (containing a Jeryl Lynn derived mumps strain RIT 4385) with a widely used vaccine, Merck MMR, when given to children between 12-24 months. Infants were divided between 2 groups; group 1 received SB MMR while group 2 received Merck MMR. Solicited local and general symptoms were recorded using diary cards and antibody levels were measured using ELISA assays. There was a significantly lower incidence of redness (p< 0.001) and swelling (p= 0.03) observed in group 1 compared with group 2. The incidence of all other solicited local and general symptoms were comparable between groups. In initially seronegative subjects equivalent seroconversion rates and post-vaccination GMTs were observed between groups. In conclusion, these results demonstrate that SB MMR is safe and well tolerated when given to children at this age range, and has an equivalent immunogenic profile compared to the widely used Merck MMR vaccine.