The scientific literature has demonstrated that probiotics have a broad spectrum of activity, although often the results are contradictory. This study provides a critical overview of the current meta-analyses that have evaluated the efficacy of probiotics in physiological and pathological conditions, such as metabolic disease, antibiotic-associated and Clostridium difficile-associated diarrhea, IBS, constipation, IBD, chemotherapy-associated diarrhea, respiratory tract infection, ventilator-associated pneumonia, NAFLD, liver encephalopathy, periodontitis, depression, vaginosis, urinary tract infections, pancreatitis, incidence of ventilator-associated pneumonia, hospital infection and stay in ICU, mortality of post-trauma patients, necrotising enterocolitis in premature infants. Only for antibiotic- and Clostridium difficile-associated diarrhea, and respiratory tract infections the effects of probiotics are considered "evidence-based". Concerning other fields, meta-analyses lacks to define type and biological effect of probiotic strains, as well as the outcome in a disease state. Therefore, the results presented should be a stimulus for further studies which will provide clinical recommendations.