Self-efficacy is one's belief in one's capacity to organize and execute a course of action and serves as a motivating factor, since people tend to seek opportunities in areas where they feel efficacious and avoid areas where they believe they might fail (Bandura, 1997). Furthermore, as language learners' feelings of efficacy increase, so does the effort they invest in language learning (Piniel & Csizér, 2013). Additionally, an effective language acquisition tool is target language reading (TLR) (Horst, 2005; Krashen, 1989, 2004; Pulido, 2007; Reynolds, 2015; Tanaka & Stapleton, 2007). Therefore, it follows that learners may benefit from further studies in TLR and perceived self-efficacy. This article presents ten principles gleaned from the writings of Bandura (1997, 2006) that provide criteria to evaluate self-efficacy scales. The article then applies these principles to five reading self-efficacy questionnaires. The article does not determine which scale is best, but it provides foreign language researchers with a set of principles by which they can identify the desired qualities and avoid common pitfalls associated with target language reading self-efficacy research. The best efficacy scale will depend upon the question the research hopes to answer; however, without guidance, many current efficacy scales fail at measuring efficacy.