• Patients with central nervous system cysticercosis show elevated binding of cerebrospinal fluid (CSF) IgG to homogenized cysticercus. To determine whether any of the CSF IgG was the result of de novo intra-blood-brain barrier (BBB) synthesis, CSF and serum samples from six patients were examined for elevated rate of synthesis and oligoclonal bands. Five of the six patients had increased intra-BBB IgG synthesis rate and four of these patients also had oligoclonal IgG bands present in the CSF that were absent in the serum. These results demonstrate intra-BBB IgG synthesis similar to that observed in other infectious and inflammatory diseases of the central nervous system.