The overuse, misuse and widespread prophylactic application of antibiotics led to the emergence of drug resistant micro-organisms and also disturb the beneficial microflora (Lactobacilli) of the body. Probiotics are live microorganisms, which, when administered in an adequate amount, confer a health benefit on the host. The most common probiotic strains belong to the genera Lactobacilli and Bifidobacterium. The purpose of the present study was to evaluate the effect of probiotic (Inersan lozenges - Lactobacillus brevis) alone, combination of probiotic with doxycycline and doxycycline alone on aggressive periodontitis, it being both a clinical and microbiological study. Probiotic has a future in the treatment of aggressive periodontitis, as most of the time, antibiotics are prescribed. These antibiotics can lead to the emergence of drug resistant micro-organisms and also disturb the beneficial microflora of the body. Thus, as an alternative to antibiotics, probiotics can be used as they repopulate beneficial microflora and reduce the pathogenic bacteria.