Objective: Pseudotumor cerebri (PTC) in children has a wide spectrum of clinical presentations, from headache, which may be posterior and associated with nausea, vomiting or diplopia, to nonspecific headache, which may not be posterior and related or unrelated to other symptoms. In children with nonspecific headache, supportive evidence for diagnosis may be required before invasive procedures such as lumbar punctures are performed. Ultrasonography of the optic nerves (USON) is a noninvasive examination that can provide information about optic nerve changes, including those resulting from increased intracranial pressure. The applicability of USON in the diagnosis and follow-up of PTC was examined. Study design: Seventeen children were referred to our service because of a clinical suspicion of PTC, suggested by the presence of swollen optic nerve discs and/or headache, without clinical evidence of another cause. All had normal brain computed tomography and/or magnetic resonance imaging results before referral. Each child was examined with USON while in the supine position and with a 30- degree head tilt and underwent a lumbar puncture. USON was repeated on follow-up evaluation. Results: The diagnosis of PTC was confirmed by lumbar puncture in 10 children and ruled out in 6 children. Overall, the USON results correlated with an increased opening pressure on lumbar puncture in 11 children. Conclusion: We noted an excellent correlation between the clinical results and the USON findings in PTC, and in many eases repeated lumbar punctures could be avoided. USON is more easily applied than a lumbar puncture, without the accompanying risks. It may be used as an indicator of increased intracranial pressure, as well as a follow-up tool. However, further studies are required before the accuracy of USON can be fully established.