514--This article focuses on the vocabulary size of 44 subjects divided into four groups according to two variables: reading (reading habit ) and language (L1 and L2). The four groups were native speakers of Spanish with reading habit (L1+reading), native speakers of Spanish without reading habit (L1-reading), non-native speakers of Spanish with reading habit (L2+reading), and non-native speakers of Spanish without reading habit (L2-reading). The results are statistically significant and show that the combination of the variables of reading and language together were predictors of 88% of the variance in the vocabulary size of the subjects, reading being the strongest predictor of the vocabulary size of the participants. In our sample, the vocabulary size of the groups were: L1+ reading (48,600), L2 + reading (40,900), L1-reading (25,500), L2-reading (11,100). A surprising result is that the L2+reading group outperformed the L1- reading group: the vocabulary size of the L2 group with reading habits was 15,000 words more than the L1 group without reading habit. This finding suggests that being a native speaker of a language does not ensure a wide vocabulary size if a person does not have a reading habit that allows them to read in big amounts and for pleasure. Similarly, it may be claimed that a strong reading habit may compensate for the condition of not being a native speaker of a language. These results, apart from supporting the incidental acquisition of vocabulary through reading, are strong evidence for the need of implementing extensive reading programs in the foreign language curriculum so that language students can acquire vocabulary incidentally through reading and the process of acquisition of a L2 can be adequately accelerated.