In search of early neuroleptic response predictors in schizophrenia, functional interhemispheric and intrahemispheric asymmetry indices, derived from spectrally analyzed resting electroencephalographic (EEG) activity, were examined in 17 schizophrenic patients prior to open label treatment with the atypical neuroleptic clozapine. Compared to EEG asymmetry indices derived from a normative data bank, patients exhibited significant interhemispheric (left greater than right) and intrahemispheric (anterior greater than posterior) deviations in delta, theta, alpha and beta frequency bands. Intrahemispheric indices were positively correlated with clinical ratings of positive symptoms and global psychopathology. Clozapine-induced improvements in positive and negative symptoms and global psychopathology symptom ratings were related to pretreatment intrahemispheric asymmetry only, with relationships varying with symptom, recording region and frequency band. The results are discussed in relation to the neurobiology of schizophrenia and the utility of EEG as an informative predictor of treatment response.