Objective: To compare the pain experienced by patients during injections of local anesthesia in the palate using the traditional syringe and the controlled flow technique with the Calaject system. Method and Materials: A single-blind, split-mouth, randomized controlled trial was performed. Twenty-five volunteers were recruited in the Dental Hospital of the University of Barcelona, Spain. Each participant received two injections (0.3 mL of mepivacaine 3%), one with the traditional syringe (control side) and another with the Calaject system (experimental side), both during the same session. Pain intensity was evaluated after each injection with a 100-mm visual analog scale (VAS). A descriptive and bivariate statistical analysis was made. Results: The mean pain experienced was 44.8 mm (standard deviation [SD] 19.0, range 8-72) with the traditional injection and 28.8 mm (SD 19.7, range 8-72) with the Calaject system (P .001). Moderate/severe pain was more frequently referred in the control side (68%) in comparison with the experimental side (28%). Conclusion: Given the parameters of this study's design, the injection of local anesthetics in the palatal area with the Calaject controlled-flow system seems to reduce pain, in comparison to the use of a traditional syringe. Palabras clave: Calaject system, computer-delivery anesthesia, dental anesthesia, local anesthesia, pain