ABSTRACT.An outline of the problems and clinical features of connective tissue disorders are given, in particular for systemic lupus erythematosus (SLE). This is the commonest of the group of rarely occurring disorders in which immunological disturbance is the basic defect. SLE, a chronic disorder, occurs mainly in women and often at a young age but in the present series with a wide age range, 18–81,mean 45 years. In the two separate groups of patients studied, disorders of the nervous system occurred in about half. Seizures, vascular episodes, and a variety of psychiatric disorders are a feature, with EEG abnormality in nearly three quarters of these. Diffuse and focal slow activity as well as slowing of the background frequencies is characteristic of the majority. In particular, evidence of focal independent areas of disturbance may be shown. Illustrative case histories are presented to exemplify some of the problems in management, for example differentiation between cerebral SLE and psychosis from steriod administration, still one of the commonest forms of treatment in connective tissue disorders. Evoked response (ER) techniques may assist in indicating the presence of various different disease sites. The EEG appears to be an important investigation in SLE since other laboratory tests are used to confirm the diagnosis of the systemic disorder rather than as evidence of CNS involvement. It is particularly useful in the management of the individual case as therapeutic endeavors are still variable.