A prospective randomized study.To compare occupational radiation exposure to the surgeon, as well as the patient, during posterior lumbar spine instrumentation in 10 navigated cases (navigated) versus 11 cases using the freehand technique (non-navigated).The use of navigation increases the accuracy of posterior lumbar instrumentation.A further speculated benefit of navigation is the reduction of radiation exposure of the surgeon. However, this has so far not been evaluated in such comparative manner.Radiation exposure to the surgeon was measured by digital dosimeters placed at the level of the eye, chest, and dominant forearm. Radiation exposure was measured from the time of positioning of the patient to the end of the procedure both for navigated (intraoperative 3-dimensional [3D] fluoroscopy-based) and non-navigated (2-dimensional fluoroscopy-guided) freehand posterior lumbar spine instrumentations. A 3D fluoroscopic scan was routinely performed at the end of the procedure for all patients.Patients were distributed evenly in the 2 groups in terms of sex, age, body mass index, and the number of operated levels. The accumulated radiation dose for the surgeon was significantly higher in the non-navigated group; up to 9.96 times. The radiation dose for the patient was higher with the freehand technique, 1884.8 cGy·cm (non-navigated) versus 887 cGy·cm (navigated), without reaching a statistically significant level.Radiation exposure to the surgeon during pedicle screw placement with the freehand technique is up to 9.96 times greater than with the use of navigation. In the latter group, the only radiation exposure comes from the preoperative-level control and positioning of the 3D C-arm before 3D fluoroscopic acquisition. Furthermore, neuronavigation also reduces the cumulative dose for the patient.2.