The authors examined relations among components of metacognition from varying theoretical perspectives, explored the psychometric characteristics of known measures of metacognition, and examined the predictive strength of measures of metacognition for both science and overall academic achievement in 97 seventh-grade students. Findings indicated expected significant correlations between 2 measures of metacognition, the Junior Metacognitive Awareness Inventory (Sperling, Howard, Miller, & Murphy, 2002) and an open-ended version of Swanson's (1990) metacognition measure and a significant correlation between the Swanson measure and general science teacher ratings of students' metacognition. Student measures demonstrated sound psychometric properties and both were significant predictors of science achievement. Additional analyses, recommendations for future research, and suggestions for practitioners and educators interested in measuring and promoting metacognition are provided. (Contains 3 tables.)