Dental caries is the major public health problem that disturbs all countries in the world. Streptococcus mutans is considered as a chief culprit of this infectious disease and biofilm formation potential is the major virulence trait of this pathogen. In the era of antimicrobial resistance it is important to understand the virulence mechanism and antimicrobial sensitivity of S. mutans globally. The objective of the study was to investigate the biofilm formation potential and antimicrobial sensitivity of clinical isolates of S. mutans. Biofilm formation potential of 100 clinical isolates was studied by microtiter plate assay and coverslip assay and antimicrobial sensitivity was assessed by disc diffusion method. Our results showed that out of 100 clinical isolates 92 (92%) showed strong biofilm forming capability and 8 (8%) clinical isolates showed moderate biofilm formation potential. Antimicrobial sensitivity results showed that 72 (72%) isolates were resistant to amoxicillin, 65 (65%) isolates were resistant to chloramphenicol, 40 (40%) isolates were resistant to doxicycline, 46 (46%) isolates were resistant to erythromycin, 32 (32%) isolates were resistant to ofloxacin, 61 (61%) isolates were  resistant to tetracycline and only 17 (17%) isolates of S. mutans were resistant to amoxicillin/clavulanate. Our results suggest that combination therapy is more effective against cariogenic S. mutans and biofilm formation potential of this organism indicates the powerful contribution in pathogenesis. Ultimately, new combination therapies and inhibitors of biofilm formation are urgently needed. Key words: antimicrobial, biofilm, dental caries, S. mutans, therapy, virulence