This study aimed at investigating the contribution of motivational beliefs, cognitive, and metacognitive strategy use to Turkish high school students' achievement in biology. In order to investigate the specified purpose of the study, 519 tenth-grade students were administered the Motivated Strategies for Learning Questionnaire (Pintrich, Smith, Garcia, & McKeachie, 1991) and a Biology Achievement Test developed by the researchers. Results of multiple linear regression analyses showed that extrinsic goal orientation, task value, rehearsal strategy use, organization strategy use, management of time and study environment, and peer learning contributed significantly to the prediction of achievement scores. (Contains 1 figure and 4 tables.)