Introduction and Objective: The main objective of the current study was to assess the pain intensity and cooperation level of the patients when using intermaxillary elastics (Class II, Class III, and Box elastic with heavy and medium forces). Methods and Materials: 134 patients were randomly assigned into two groups of medium and heavy elastics. The study included measuring the pain and cooperation with heavy and medium forced elastics. The cooperation level was assessed using the questionnaire for cooperation. The severity of the pain was recorded using the visual analog scale (VAS) on the first day (at three intervals of two hours, six hours after receiving elastic and at the end of the night) and one, four and fourteen days after receiving the elastics. Results: From 67 patients in each group, 55 patients of the medium group and 57 patients of the heavy group completed the questionnaires. Assessing the effects of the type of elastics, i.e. medium or heavy, on the mean pain intensity at each time interval, showed that while the clinical pain intensity in the group of medium-forced elastic is lower than the other group, this difference is not statistically significant (except on the 4th day, p=.018). Assessing the level of cooperation, showed that there is no significant difference between the two groups of patients. Conclusion: The pain intensity was lower in the medium group; but, the difference was not statistically significant. Comparing the pain level among various types of elastics, i.e. Class III, Class II, and the Box elastic, does not reveal a significant difference (except for the 4th and 14th days). The cooperation level was similar in both groups.