Aim: In patient with necrotic immature anterior teeth with open apecies and periapical abscess, this study was done to find whether or not the revascularization is more effective than MTA apexification in the following: 1. Resolution of pain: Measured with modified Visual Analog Scale (VAS). 2. Resolution of periapical radiolucency: Binary Outcome. 3. Increase in root length: Measured in mm. 4. Increase of dentin thickness: Measured in mm. 5. Decrease in apical diameter: Measured in mm. Method : Twenty two patients suffering from necrotic immature anterior teeth with open apecies were randomly assigned into two equal groups with 11 patients each. One group was treated by regeneration and the other by MTA apexification. Cases were assessed: Clinically by measuring pain with modified visual analogue scale (VAS), and assessing swelling presence. Radiographically by digital radiography and parallel technique for more standardized results that allow accurate measurements of changes in root length, dentine thickness, and apical diameter. Results : Results showed there was no statistically significant difference between the two groups in pain preoperative VAS scores, after 4 hours, after 12 hours, after 24 hours and after 48 hours in first and second visits and no statistically significant difference was found between the two groups in 1 month, after 3 months, after 6 months, after Summary and Conclusion : 9 months and after 12 months. Also showed that the percentage of healing of radiolucency is higher in regeneration group (90.9 %) than MTA apexification group (63.6 %) which showed high percentage of success. Also showed that the percentage of healing of swelling is higher in regeneration group (81.8 %) than MTA apexification group (72.7 %) which showed high percentage of success, But there was a statistically significant difference in pain in the regeneration group between (12 hours) group on one hand and each of (4 hours) and (48 hours) groups in the second visit on the other hand where (p=0.03) and (p=0.008) respectively. Also a statistically significant difference in pain was found between (24 hours) and (48 hours) groups in second visit where (p=0.02). It also showed that regeneration group showed better results in increase in root length and in increase in dentin thickness in mm and in percentage although there was no statistically significant difference between MTA apexification group and regeneration group. On the other hand, MTA apexification group showed better results in decrease in apical diameter in mm and in percentage although there was no statistically significant difference between MTA apexification group and regeneration group. Conclusion : 1- Both regeneration and MTA apexification are reliable procedures for treating necrotic immature anterior teeth with open apecies except that regeneration is preferable. 2- Regeneration has a higher rate of success concerning resolution of swelling and radiolucencies. 3- Regeneration is superior in adjusting crown-to-root ratio.