BACKGROUND The purpose of this study was to investigate the success rate of midpalatal miniscrews used for orthodontic anchorage and the factors affecting clinical success. METHODS One hundred twenty-eight consecutive patients (101 female, 27 male; mean age, 23.4 years), who received a total of 210 miniscrews in the midpalatal suture area, were examined. Success rates were determined according to 10 clinical variables. RESULTS The overall success rates were 88.20% for the total number of patients and 90.80% for the total number of miniscrews. There were no significant associations among success rate and sex, total period of treatment with miniscrews, diameter of miniscrews, types of tooth movements, and variables that represent sagittal and vertical skeletal relationships (ANB, FMA, and Sn-GoGn). The operator's learning curve, patient's age, area (midpalatal or parapalatal), and splinting significantly influenced the success rates. After adjusting for other variables, only 1- splinting-showed a significant effect on the success rate. CONCLUSIONS The joining of 2 miniscrews by splinting, placement of the miniscrew in the midpalatal suture, patient's age (especially >15 years), and operator's skill were factors influencing the clinical success of orthodontic miniscrews in the palate.