Visual similarity effects during the early stages of word processing have been consistently found for letter-like digits and symbols. However, despite its relevance for models of word recognition, evidence for letter visual-similarity effects is scarce and restricted to behavioral experiments. In two masked priming experiments, we measured event-related potential (ERP) responses to words preceded by an identical (dentist-DENTIST), a visually similar (dentjst-DENTIST), or a visually dissimilar prime (dentgst-DENTIST) to track the time course of the effects of letter visual-similarity during word processing. In the 230-to 350-ms time window, the ERPs in the visual dissimilar condition showed larger negative-going amplitudes than in the visual similar condition, which in turn behaved like the identity condition. In a later time window (400-500 ms), the visually similar condition elicited larger negative-going amplitudes than the identity condition. This pattern of findings can be accommodated within those models of word recognition that assume uncertainty concerning letter identities early in word processing that is resolved over time. Keywords Word recognition. Event-related potentials. Lexical decision. Masked priming The process of visual word recognition in skilled readers involves extremely efficient mechanisms that, in a few hundreds of milliseconds, convert the visual signal into the appropriate long-term lexical representation despite the similarity between letters (e.g., prescribe, but not the visually similar word proscribe) (see Grainger, 2018; Grainger, Dufau, and Ziegler, 2016, for recent reviews). However, visual similarity among stimuli seems to influence this process. Previous research has shown that sentences in which some of the letters are replaced by similar symbols or digits (e.g., MΔT3R1ΔL 7H1NGS C0M3 ΔND G0) can be read without much cost (Duñabeitia, Perea, and Carreiras, 2009). Indeed, a number of experiments using Forster andDavis'(1984) masked priming technique (i.e.,a procedure that taps the initial stages of word processing; Grainger, 2008) have consistently reported facilitative effects of visual similarity with letter-like digits and letter-like symbols during word recognition. In the initial demonstration of the effect, Perea, Duñabeitia, and Carreiras (2008) found faster lexical decision times to a target word like MATERIAL when preceded by a prime with similar letter-like digits (M473RI4L) or symbols (MΔT€R!ΔL) than when preceded by a dissimilar prime (M568RI2L or M□T%R?□L). Furthermore, Perea et al. (2008) found that visually similar primes were nearly as effective as the identity primes (see also Kinoshita, Robidoux, Mills, & Norris, 2013; Perea, Duñabeitia, Pollatsek, & Carreiras, 2009, for converging behavioral evidence). Molinaro, Duñabeitia, Marìn-Gutiérrez, and Carreiras (2010) used event-related potentials (ERPs) to examine the time course of visual similarity effects with words containing similar letter-like digits. In their masked priming experiment, targets that were prece...