Object. Tethered cord release for a tight filum terminale is a common pediatric operation associated with low morbidity and mortality rates. While almost all would agree that keeping patients lying flat after the operation will prevent a CSF leak, the optimal period of doing so has not been determined. In this study, the authors examined whether a longer length of stay in the hospital for the sole purpose of maintaining patients flat correlates with a decreased rate of CSF leakage. Methods. Intraoperative and postoperative data were retrospectively collected in 222 cases of simple tethered cord release at 3 large children's hospitals. Risk factors for postoperative CSF leakage were identified. Results. Thirty-eight patients were maintained lying flat for 24 hours, 86 for 48 hours, and 98 for 72 hours at the individual surgeon's discretion. A CSF leak occurred in 13 patients (5.9%) and pseudomeningocele developed in 9 patients (4.1%). In the univariate analysis, operating time, use of the microscope, use of dural sealant, and duration of remaining flat after surgery failed to correlate with the occurrence of complications. Conclusions. A longer hospital stay for maintaining patients flat after a simple tethered cord release appears not to prevent CSF leakage. However, a larger patient cohort will be needed to detect small differences in complication rates.