Background and Objective: There are indications that acute myocardial infarction (AMI) may have an effect on the oral environment, which is reflected in the expression of salivary and gingival proteinases. According to our knowledge, no studies have been carried out to investigate the effect of AMI on the activities of two major tissue-destructive serine protease and microbial effectors, elastase and cathepsin G, produced by oral fluid polymorphonuclear granulocytes (PMN). Therefore, we compared the activities of elastase and cathepsin G in saliva from patients with AMI and from systemically healthy subjects (non-AMI) with similar periodontal conditions. Material and Methods: A total of 92 patients (47 AMI and 28 non-AMI patients with gingivitis or periodontitis, and 17 systemically and periodontally healthy subjects as a control group) were recruited. Clinical periodontal measurements were recorded, and stimulated whole-saliva samples were collected. The patients with AMI were clinically examined within 3-4 d after admission to the coronary care unit. The activities of saliva neutrophil elastase and cathepsin G were measured after collection, at specific time-points during incubation (from baseline to 23 h) by specific synthetic peptide substrate assays. Results: The saliva of patients with AMI and periodontitis had a significant trend for the highest elastase activities among the study groups. Elastase and cathepsin G activities correlated significantly with each other in the AMI periodontitis group (r = 0.8, p < 0.01). In a logistic regression analysis, the level of salivary elastase activity associated significantly with periodontitis. Conclusion: AMI may be reflected in PMN serine protease elastase activity in saliva, despite its strong association with periodontitis.