This study analyzed the Trends in International Mathematics and Science Study 2011 data on fourth-grade U.S. students' mathematics performance to answer four research questions: (a) How did U.S. students' geometry performance compare with their performance on the other mathematics subscales? (b) What were the patterns of student achievement among the mathematics subscales? (c) Was there a group of students who demonstrated specific difficulties in geometry only? and (d) Which demographic variables contributed to students' classification in the group with geometry difficulties? We found that (a) U.S. students' performance was poorer on the Geometry subscale than on other mathematics subscales; (b) using latent profile modeling, we identified a group of students with the lowest scores across all three mathematics subscales who showed a significant discrepancy between Geometry and the other subscales that did not exist within the high-achieving and average-achieving groups; and (c) gender, age, home language, race, and preference for mathematics and science significantly influenced the probability of being classified in the group with the lowest performance and the largest gap between Geometry and other mathematics subscales. Implications for educational theory and practice are discussed.