SUMMARY OBJECTIVE: This study aims to evaluate the relationship between periodontal health status and coronary slow flow phenomenon. METHODS: One hundred and two patients who underwent coronary angiography with the diagnosis of stable angina pectoris were included in the study. Patients were divided into two groups: patients with coronary slow flow (Test group) (n=51), and patients with normal coronary angiography (Control group) (n=51). Diagnosis of slow coronary flow was made according to Beltrame criteria by coronary angiography. Demographic characteristics of the participants were recorded. The periodontal health was assessed by clinical periodontal parameters such as probing depth, clinical attachment level, gingival index, plaque index, and bleeding on probing. RESULTS: There were no significant differences between groups as regards the frequencies of hypertension, smoking (p>0.05). As for the periodontal parameters of the study groups, probing depth, gingival index, plaque index, bleeding on probing, and clinical attachment level values were statistically higher in the test group compared to the control group (p<0.05). CONCLUSIONS: Periodontitis might be accepted as one of the underlying causes of coronary slow flow. Patients with coronary slow flow should be evaluated for an underlying periodontal disease, and treatment of periodontal disease can protect against future cardiovascular events.