We present a new mega-study (called MEGALEX) involving the collection of visual and auditory lexical decision data for 28,000 French words and the same number of pseudowords. This new mega-study applied the repeated measures design developed by Keuleers, Lacey, Rastle, and Brysbaert (2012). For each modality tested (visual vs. auditory), two groups of 40 participants each responded to 14,000 words and the same number of pseudowords for a total duration of 20h (divided over multiple sessions). Collected reaction times were submitted to multiple regression analyses in order to study the influence of continuous lexical variables such as word frequency, word length (in letters), and orthographic similarity. We compared the different modalities. We also compared the visual data with those obtained in another French mega-study using a more classic design, the French Lexicon Project (Ferrand, New, Brysbaert, Keuleers, Bonin, Méot, Augustinova, & Pallier, 2010).