ABSTRACT Objectives: The aim of the present study was to evaluate and compare the Microbial and periodontal changes associated with conventional versus self ligating brackets. Methods: The current randomized clinical study was conducted on a total sample of 30 orthodontic patients. The sample with mean age 16 Y. The patients were divided in to three groups, Group I: Include 10 patients treated with conventional stainless steel orthodontic brackets ligated with stainless steel ligature. Group II: Include 10 patients treated with passive self-ligating stainless steel orthodontic brackets Group III: Include 10 patients treated with active self-ligating stainless steel orthodontic brackets. Periodontal and microbial parameters were taken for each patient at baseline and at monthly interval for 6 months. The data were collected, tabulated and statistically analyzed to compare the changes within each group and among the three studied groups.  Results: The results showed significant increase in microbial and periodontal parameters in the three studied groups and among the studied groups. Active self ligating brackets caused more periodontal and microbial changes than either passive self ligating or conventional brackets. Conclusion: orthodontic alignment with both conventional and self ligating brackets causes variable amounts of microbial and periodontal changes. Active self ligating brackets causes more changes in microbial, plaque and bleeding indices than either passive self ligating or conventional brackets, however, pocket depth changes were almost similar in the three groups.