Nitric oxide (NO) affects both pain and inflammation in human tissues. Pharmacotherapy that decreases NO concentrations may have utility in treating inflammatory painful conditions. To determine the types of disorders in which such an approach should be studied, changes in NO serum levels before and after the painful inflammatory condition resolves would be helpful. This study compared the pre-treatment and post-treatment serum nitric oxide (NO) concentrations in irreversible pulpitis (inflammatory toothache). Thirty-two patients (16 males, 16 females) with irreversible pulpitis were included in this study. Before treatment, patients had severe symptoms of inflammation, but at the end of treatment no symptoms of inflammation were observed. NO concentrations were measured in serum of patients with irreversible pulpitis, before and after treatment. Differences in serum NO concentrations were not statistically significantly different before and after treatment.