Because of the tradition of using honey as an antimicrobial medicament, we investigated the effect of natural honey (NH) on Streptococcus mutans growth, viability, and biofilm formation compared to that of an artificial honey (AH). AH contained the sugars at the concentrations reported for NH. NH and AH concentrations were obtained by serial dilution with tryptic soy broth (TSB). Several concentrations of NH and AH were tested for inhibition of bacterial growth, viability, and biofilm formation after inoculation with S. mutans UA159 in 96-well microtiter plates to obtain absorbance and CFU values. Overall, NH supported significantly less (P < 0.05) bacterial growth than AH at 25 and 12.5% concentrations. At 50 and 25% concentrations, both honey groups provided significantly less bacterial growth and biofilm formation than the TSB control. For bacterial viability, the results for all honey concentrations except 50% NH were not significantly different from those for the TSB control. NH was able to decrease the maximum velocity of S. mutans growth compared to AH. In summary, NH demonstrated more inhibition of bacterial growth, viability, and biofilm formation than AH. This study highlights the potential antibacterial properties of NH and could suggest that the antimicrobial mechanism of NH is not solely due to its high sugar content.H oney has been used as a source of nutrients as well as a medicine since ancient times (3). Recent publications indicating the effect of honey in the management of certain conditions have rekindled interest in honey as a natural therapeutic agent. For example, honey can be used as a temporary dressing in burns (20). It has also been found to be effective in the management of radiation-induced mucositis in patients receiving head and neck radiotherapy (26). In addition, Robson and colleagues recorded accelerated healing when honey was used as a wound dressing material in a randomized clinical trial (28).The antibacterial properties of honey have been well documented (37). However, the specific antimicrobial mechanism of honey is still unclear (7). Among the possible mechanisms are the presence of inhibitory factors such as flavonoids (16) and hydrogen peroxide (35, 36), low pH (38), and high osmolarity due to its sugar concentration (38).Honey may have a similar antibacterial effect on Streptococcus mutans, which is considered the main causative organism of dental caries (21). S. mutans along with other oral bacteria forms on the tooth surface a microbial community surrounded by extracellular matrix and salivary proteins (22), collectively known as dental biofilm. Cariogenic bacteria within this biofilm utilize dietary sugars and produce lactic acid as a by-product (34). This acid attacks and demineralizes the tooth structure, leading to decay.Very limited studies have investigated the effect of honey on S. mutans. These studies investigated the effect of honey on several strains of oral bacteria (7). Here, we tried to explore the effect of honey on the growth and viability of S. mutans...