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Temporal fluctuations in speech are of major importance for speech intelligibility. In normal listening situations, the speech envelope alone is sufficient for accurate speech intelligibility. The speech envelope consists of modulations and fluctuations at frequencies mainly below 20 Hz. The auditory steady-state response (ASSR) method is ideal to objectively measure the auditory pathway's response to speech-envelope- like fluctuations (0.5-20 Hz). ASSRs are stationary responses that are elicited by periodically varying or modulated sounds. A unique feature of ASSRs elicited by speech-envelope-like fluctuations is that they origin from the auditory cortices. As a result, auditory processing can be studied at the highest level of the auditory pathway. However, due to the clinical relevance for threshold determination, most studies focused on subcortical and brain stem ASSRs. Few studies have investigated cortical ASSRs. In order to interpret cortical ASSRs for studying speech processing knowledge about test-retest repeatability, and inter- subject variability of these responses is of major importance. We studied the test-retest repeatability and inter-subject variability of cortical ASSRs with a 64-channel EEG set-up in ten young adults during two test sessions. During each test session, ASSRs were measured for 30 modulation frequencies ranging from 0.5-20 Hz with a 0.5-1 Hz step size. A 70 dB SPL, 100% modulated, 1 kHz one-octave band white noise stimulus was used. Results show unique underlying subject dependent synchronized activity patterns. The underlying synchronized activity patterns were, for all subjects, highly reproducible across test sessions. [ABSTRACT FROM AUTHOR]