The aim of this study was to evaluate the effect rubber dam placement on the arterial oxygen saturation level in children. Thirty children were randomly allocated to one of two groups: Group A-15 patients in this group had rubber dam isolation of the maxilla, and Group B-15 patients had rubber dam isolation of the mandible. The children were healthy and cooperative. The arterial oxygen saturation was taken before each injection, before starting the intervention, i.e. 5 min after the injection, and at 5-min intervals. All SpO 2 values were recorded every 30 seconds over a 30 minute period. There were no statistically significant differences in arterial oxygen saturation in all reading sessions for both groups (P>0.05). The use of rubber dam did not decrease the arterial oxygen saturation level in children. smooth muscle may survive for several days without oxygen 6). This has important implications in the management of oxygen transport and monitoring of tissue hypoxia in medically-compromised patients. Therefore, hypoxia should be a concern in dental procedures, especially in medically-compromised patients and children. Goodday and Crocker 7) evaluated the effect of rubber dam placement on arterial blood oxygen saturation in dental patients. They found no significant change in arterial blood oxygen saturation (SpO 2) before and after rubber dam isolation. There are few studies evaluating the effect of rubber placement dam on arterial oxygen saturation in children and its effect on children has not been studied extensively 8,9). The purpose of this study was to evaluate the effect rubber dam placement on the arterial oxygen saturation level in children. Materials and Methods Participants, including 17 boys and 13 girls ranging between 4 and 12 years of age (mean age 7.6 years) were selected from the patient population at the