This study investigates socio-cultural cognitive literacy predictors for reading literacy (RL), tested in 314 fourth graders from two different levels of social economic status in Lima, Peru. The following variables were tested as predictors: word decoding, vocabulary, motivation to read, reading strategies, intellectual maturity, gender, home literacy climate and social economic status. RL (reading literacy) was measured using an adapted version of the PIRLS Reading Literacy test. By using structural equation modelling, a total of 34 percent of the variance in RL could be explained. In addition to word decoding and vocabulary, motivation and social economic status were discovered to be directly predictive of RL. Furthermore, social economic status and home literacy climate were discovered to be important factors in determining the variation in other predictor variables. Intellectual maturity and gender did not appear to be significant factors contributing to RL level.