The aim of the trial is to evaluate safety of a follow on formula supplemented with Lactobacillus salivarius CECT5713. A randomized double blind placebo controlled trial was carried out. Eighty six months old children were recruited by the department of pediatrics of Hospital Univeristario San Cecilio. Children were divided in two groups that consumed a follow on formula supplemented or not with the probiotic strain during 6 months. Fecal samples were obtained at the recruitment, at 3 months and at the end of the trial. In addition revision by the pediatrician was performed once a month and possible adverse effects were recorded both by the pediatrician and by parents.