PURPOSE Psychosomatic indicators, such as heart rate (HR), salivary alpha amylase (sAA) activity, and behavior, can be used to determine stress. This study's aim was to assess the pattern of changes of salivary alpha amylase, heart rate, and cooperative behavior in previously naïve children receiving dental treatment under local anesthesia. METHODS Included were 30 children with no prior dental experience who needed 4 or more sessions of dental treatment involving local anesthesia. In each session, sAA, HR, and behavior were assessed before and during the application of local anesthesia and at the end of the treatment. RESULTS The highest sAA value was always observed at the end of each session; overall, the value was lower in the fourth session. HR always increased during the local anesthesia, and did not vary across sessions. No significant relationship was found between child cooperation and either sAA or HR. CONCLUSION In this sample, child cooperation may not be an accurate indicator of stress. Based on salivary alpha amylase activity changes, dental treatment involving local anesthesia in naïve children appeared to be less stressful after 3 sessions.