Probiotics produce a beneficial impact on the host by improving the endogenous flora. It has been advocated that nonpathogenic bacteria like Lactobacillus and Bifidobacterium may undergo antagonistic interactions with other bacterial strains and can be used to control pathogenic bacteria. Novel modes of therapeutic and prophylactic interventions are based on their consumption either alone or in combination with prebiotics. Usefulness of probiotics has been implicated in allergies, cancer, AIDS, and respiratory and urinary tract infections. In this review we have listed various findings suggesting their benefits in alleviating symptoms associated with aging, fatigue, and autism. Newer claims indicating their role in reducing the risks of osteoporosis, obesity, and possibly type 2 diabetes are also discussed. Considering the wide array of such activities, the present review comprehensively elaborates upon the proposed benefits of probiotics. The concept of synbiotics, a combination of probiotics and prebiotics beneficially affecting the survival and implantation of such live organisms, is also discussed. Available probiotic strains, their commercial preparations, and newer approaches to improve the efficacy and overcome limitations of the therapy are also discussed in relation to the future of probiotic therapy. Considering that the purported claims about disease risk reduction are tentative, the review also encompasses various aspects regarding the safety of probiotics and their possible future role in disease prevention.