Nervous system involvement in patients with AIDS is frequent either due to direct infection by the HIV-1 or to opportunistic infections or neoplasms. In the present study we evaluate the epidemiologic characteristics of patients in whom the first AIDS manifestation was an indicative neurologic disease (IND) and the influence of such a presenting form in the patients' survival. Out of 1250 reported cases, 252 (20.2%) presented with one of the INDs, according with the CDC AIDS definition criteria. Neither sex nor age differences were found between patients presenting with and without an IND. IVDUs were more likely to present with an IND than homosexual/bisexual men (p = 0.024). Cerebral toxoplasmosis (CT) was the only IND with a significant proportional increase over time. Although some of the IND have a specific treatment, as a whole patients presenting with an IND lived shorter than those presenting with any of the other indicative disorders (p less than 0.0001). The incidence of IND is greater than elsewhere, mainly because of CT. The increment of CT may be in part due to the introduction of the new AIDS definition criteria.