Changes in achievement motivation over the first semester of university studies were examined with N = 229 freshmen, who were surveyed twice in the present study. Students' academic self-concepts, achievement goals, and subjective values were chosen as theoretically central components of achievement motivation. The results indicated significant deterioration in achievement motivation over the course of the first semester of university studies, a phenomenon which affected a large proportion of the first-year students. Regression analyses provided evidence that motivation, prior to the start of university studies, and the changes in motivation had incremental validity over measures of prior school-achievement in predicting self-regulated learning, performance in examinations, as well as the intention to change university majors or drop out completely (partially in interaction with prior school-achievement).