Diploma Thesis Title: Finding the evidence about efficacy and safety of probiotics for the prevention of pediatric antibiotic-associated diarrhea: systematic review approach Objectives: To find the best available evidence of efficacy and safety of probiotics for the prevention of pediatric antibiotic-associated diarrhea. Material and Methods: „Probiotics for the prevention of pediatric antibiotic-associated diarrhea“ systematic review was found by searching the Cochrane Library website. Further, MEDLINE (PubMed), DARE and CENTRAL databases were searched in order to find new randomised controlled trials and systematic reviews, following the same criteria that were used in Cochrane systematic review. After the search for studies was done, we made quality assessment of all systematic reviews using R-AMSTAR tool. Results: According to the Cochrane systematic review, the results of the analysis indicate that probiotics may be effective in preventing AAD (RR of 0.52, 95% CI 00:38 - 0.72, I2 = 56%). After ITT sensitivity analysis that was conducted using random-effect models, the benefit of probiotics in preventing AAD was not statistically significant (RR 0.81, 95% CI 0.63 - 1.04, I2 = 59%) while the ITT subgroup analysis was marginally significant for high dose probiotics. None of the 11 trials that reported on adverse events documented any serious adverse events. We found 3 new RCTs which clearly state the existence of significant differences between the groups with probiotic and control groups. Results of two studies undeniably highlight the effectiveness of probiotics in preventing and reducing the risk of AAD (RR = 0.419, 95% CI 0.217 - 0.808; P = 0.008). In a third study, results show that probiotics are effective in the prevention and treatment of diarrhoea and AAD shortening the duration of diarrhea (P <0.001) and reducing the frequency of stools (P <0.05). In 2 of 3 studies no adverse events associated with the use of probiotics were observed while the third study reported some mild and rare side effect. More recent Cochrane systematic review provides evidence of moderate quality that confirmed that probiotics may be effective in preventing AAD (RR 0.46, 95% CI 0.35 - 0.61). Lactobacillus rhamnosus or Saccharomyces boulardii at 5 to 40 billion CFU/day may be appropriate given the modest NNT and the likelihood that side effects are very rare. Although no serious adverse events were observed among otherwise healthy children, serious side effects have been observed in severely debilitated or immuno-compromised children with underlying risk factors including central venous catheter useas. Both Cochrane systematic reviews concluded that it is to early to draw conclusions about the efficacy and safety of other probiotic agents for pediatric AAD. Total R-AMSTAR score for the first Cochrane systematic review was 37 and for the second 35. Conclusion: Based on the reviewed systematic reviews and randomized controlled trials, there is no enough evidence supporting efficacy and safety of probiotics for the prevention of pediatric antibiotic-associated diarrhea.