The aim of this work is to verify a correlation between the grade of inflammation and the concentration of PGE₂ in human dental pulp. A total of 25 human dental pulps were examined by histological analysis and radioimmunologic dosage of PGE₂. The pulps used in this experiment were from healthy and symptomatic teeth; the first ones were collected from teeth destined to be extracted for orthodontic reasons. An increase was observed of PGE₂ in reversible pulpitis compared with healthy pulps and with the irreversible pulpitis and the clear decrease of these when NSAIDs are taken. This study demonstrates that PGE₂ level is correlated to histological analysis thus allowing to distinguish symptomatic teeth in reversible and irreversible pulpitis.