Abstract: In foreign language reading, a hyperlexic reader is not hard to find. Few studies are however, devoted to this phenomenon. This article probes such readers for the causal factors. It proposes that readers' prior knowledge and its strategic use, and cognitive mechanisms like suppression and working memory capacity are all contributors to a hyperlexic reader. As for reading in a second language, this could be explained by the threshold effect resulting from the combined effects of L2 proficiency level and cognitive mechanisms like suppression and L2 working memory. Due attention should be given to develop L2 learners' lexical and grammatical knowledge, and to minimize the influences on L2 reading and processing of conceptual restructuring in L2 vocabulary acquisition. The article ends by suggesting interventions with readers' hyperlexic difficulty through reading strategy training, explicit teaching of L2 vocabulary, and repeated corrections in learners' language output.