Cysticercosis of the central nervous system, because of the combination of inflammatory response, topography of lesions, degree of parasitic infestation, and sequelae of previous infestations produces a most variable clinical picture. The symptomatology may range from a discrete neurological disturbance to the most dramatic brain disorder. Severity of the disease, prognosis, and medical or surgical decision for treatment largely depend on the individual amalgam of the above-referred factors. An improved classification of neurocysticercosis (NCC) that delineates active from inactive forms of the disease will eventually be important in the research of immunodiagnosis and in therapeutic trials. In this report, a classification is presented that separates active from nonactive forms of NCC and is based on our experience with 735 patients studied. Characteristics of each form of NCC, frequency of principal signs and symptoms, and findings in cerebrospinal fluid analysis are discussed.