A fundamental issue in cognitive neuroscience is the existence of two major, sub-lexical and lexical, reading processes and their possible segregation in the left posterior perisylvian cortex. Using cortical electrostimulation mapping, we identified the cortical areas involved on reading either orthographically irregular words (lexical, "direct" process) or pronounceable pseudowords (sublexical, "indirect" process) in 14 right-handed neurosurgical patients while video-recording behavioral effects. Intraoperative neuronavigation system and Montreal Neurological Institute (MNI) stereotactic coordinates were used to identify the localization of stimulation sites. Fifty-one reading interference areas were found that affected either words (14 areas), or pseudo-words (11 areas), or both (26 areas). Forty-one (80%) corresponded to the impairment of the phonological level of reading processes. Reading processes involved discrete, highly localized perisylvian cortical areas with individual var)