This dataset contains the raw EEG, clinical, and demographics information from a total of 38 patients with schizophrenia, with an age- and sex-matched control sample of 39 healthy individuals. Raw EEG data was collected at 1000 Hz sampling with a 64-channel Neuroscan amplifier. For more details on data collection and population characteristics, please see Reduced temporal variability of cortical excitation/inhibition ratio in schizophrenia by Racz et al., 2025 (DOI: https://doi.org/10.1038/s41537-025-00568-3). Furthermore, the pre-processed data analyzed in this study along with analysis codes is available at the GitHub repository https://github.com/samuelracz/schizophrenia_EI_variability. In case of any questions, please feel free to contact the authors at csukly.gabor@semmelweis.hu or fsr324@austin.utexas.edu. When using this resource, please cite Racz, F.S., Farkas, K., Becske, M. et al. Reduced temporal variability of cortical excitation/inhibition ratio in schizophrenia. Schizophr 11, 20 (2025). https://doi.org/10.1038/s41537-025-00568-3