Neurocysticercosis (NCC), which is caused by infection with the larval stage of the pork tapeworm (Taenia solium), is now recognized as a major cause of neurologic diseases in countries where the infection is endemic. Migration of persons from these countries is resulting in diagnosis and local transmission in nonendemic countries at increasing rates. In the present study, immunoblotting and an ELISA were carried out using antigens of T. solium cysticerci fractionated by isoelectric focusing and serum samples from patients with NCC, alveolar (AE) or cystic echinococcosis (CE), and other diseases. Immunoblot analysis revealed antigens fractionated by isoelectric focusing (pH 9.2-9.6) either from cyst fluid of T. solium cysticerci or from intact cysts had unique components (glycoproteins) highly specific and sensitive for detection of NCC exclusively. All confirmed NCC serum samples (53 of 53) recognized at least three major bands of 10-26-kD of fractions with pH 9.2-9.6 from either intact cysts or cyst fluid. These bands were not recognized by sera from patients with other parasitic diseases including AE (0 of 34), CE (0 of 36), or other heterologous parasitoses (0 of 77), patients with hepatoma (0 of 19) or sarcoidosis (0 of 11), or sera from healthy controls (0 of 29). The ELISA using the antigens showed the same sensitivity and specificity for differentiation of NCC (53 of 53) from other diseases (0 of 107) or healthy individuals (0 of 29). Both immunoblotting and the ELISA using the fractionated antigens readily differentiated all NCC from AE or CE in a blind test of 29 serum samples of persons with NCC, CE, and AE. Antigens fractionated from cyst fluid of T. solium cysticerci by a simple, single-step isoelectric focusing (pH 9.2-9.6) are highly specific and sensitive for differential serodiagnosis of NCC in immunoblotting and/or an ELISA.