Using animated computer-generated graphics to assist instruction has recently attracted the attention of educators and educational researchers. The specific focus of this study is to compare the influence of animated visuals with static visuals on college students' understanding of organic reaction mechanisms in chemistry. This study also focuses on the relationship between students' achievement and spatial ability. The results demonstrate that students using animated visuals performed significantly better than students using static visuals, who in turn performed significantly better than a control group with respect to knowledge of organic reaction mechanisms. A positive correlation was found between students' spatial ability and their achievement in organic chemistry. The results also indicate that students with high spatial ability gain more by viewing the kinetic visualizations. (Contains 3 tables, 1 figure, and 3 notes.)