The current studies introduce the goal attainment expectancy construct to achievement goal theory. Three studies, 2 in college classrooms and the other using a novel math task in the laboratory, converged on the same finding. For mastery-approach goals and performance-approach goals alike, the harder the goal appeared to attain, the less likely participants were to pursue it, ultimately with negative repercussions to participants' task interest and achievement. Additionally, in each study, mastery-approach goals were generally considered easier to achieve than performance-approach goals. Study 3 also demonstrates that these judgments are highly amenable to cues in the situation: Mastery-approach goal expectancies are colored by the apparent complexity of the material to be learned. Multiple theoretical implications are considered, particularly for work on achievement goal antecedents and goal revision. (Contains 4 tables, 3 figures, and 13 footnotes.)