The prediction of reading and writing acquisition has been the subject of numerous research studies, given the importance of the issue. Phonological processing skills and rapid automatic naming are among the best predictors in most research studies. However, many of the results have been obtained in languages other than Spanish, and from studies that assess these skills in children who are already readers. Therefore, the relationship between reading and writing and other skills could be the result of learning these skills. The aim of this study was to identify variables that predict the acquisition of mechanical reading and writing in Spanish. A group of 50 pre-reading children participated in different tasks (phonemic awareness, pseudoword repetition, memory span, verbal fluency and Rapid Automatic Naming), and eighteen months later, when they could read and write, literacy skills were evaluated. Pearson correlations, factor analysis, and linear regression analysis were carried out on the data. Phonological awareness was the variable that best predicted reading accuracy and writing, while rapid automatized naming of pictures predicted reading speed. These data indicate that it is possible to predict the acquisition of reading and writing skills before they are taught. Furthermore, these results suggest that early intervention is possible, especially in those children who are at risk of learning difficulties.