OBJECTIVE: To evaluate the effect of medical cannabis consumption on oral flora and saliva. DESIGN: A clinical prospective study, at the rheumatology clinic of the Nazareth Hospital in Nazareth, recruiting consecutively patients approved for medical cannabis, evaluating their saliva flow, pH and microbial load of Streptococcus mutans and Lactobacillus, prior to and under medical cannabis treatment. METHODS: Patients recently licensed for medical cannabis treatment, were recruited just prior to starting medical cannabis consumption (week 0), 1 and 4 weeks later, patients provided 5-minute time saliva samples, which were measured for their volume and pH, and cultured on a special microbial kit, evaluating the growth of Streptococcus mutans and Lactobacillus. RESULTS: Out of 16 patients enrolled, 14 were female and had fibromyalgia. The mean age of the patients was 52.8±12.9 years. The mean saliva flow at week 0, week 1 and week 4 were 5.38±3.36 ml/5-minutes, 6 (p = 0.769) and 5.45 (p = 0.391), respectively, and for saliva pH were 6.28, 5.94 (p = 0.51) and 5.5 (p = 0.07) respectively also. The mean Streptococcus mutans growth score at weeks 0, 1 and 4 was1.8±0.75, 1.6±0.83 (p = 0.234), and 2.4±0.84 (p = 0.058), respectively. The mean Lactobacilli growth score at weeks 0, 1 and 4 was 2.59±0.88, 3.1±0.69 (p = 0.033) and 3.3±0.67 (p = 0.025), respectively. CONCLUSIONS: The results of this study show that medical cannabis consumption has no significant effect on saliva volume or pH, but it may be associated with changes in salivary levels of oral microbes such as Streptococcus mutans and Lactobacilli.