Central nervous system (CNS) dysfunction in patients with systemic lupus erythematosus (SLE) is highly variable, although it is often described under a single heading of "neuropsychiatric" or "CNS" SLE. To clarify these CNS abnormalities, we studied 91 lupus patients, 63 of whom had CNS symptoms or signs, over 599 patient years. By placing patients in relatively homogeneous clinical groups (stroke, seizure, suicide attempt, hallucination, confusion, decreased alertness) we detected significant (but variable among groups) correlations with other manifestations of SLE, suggesting separate mechanisms for each CNS disorder. These correlations were lost if all "CNS-SLE" was considered as a single group. Patients with decreased alertness often had undetected systemic infections and had a high death rate from infection, rather than from CNS-SLE. The understanding of the pathogenesis and potential treatment of CNS disorders in lupus will depend on classifying the patients into homogeneous groups.