This study explores different variables leading to proficiency in English as a second language. Level of English on a placement exam taken upon entering a private university in Mexico was correlated to several variables. Additionally, participants (N = 218) were asked their perception of their own proficiency. A linear regression and a one-factor ANOVA were carried out. Three variables best explain the level obtained on the placement exam. These are: number of instruction hours, type of school, and how frequently the learner reads in English. Findings also show that the participants' perception of their proficiency corresponds to the results obtained on the placement test.