Although autonomy-supportive teaching has been linked with increased student performance, this contention has not yet been explored in an experimental study. This article presents a small, pre/post control group experimental study evaluating the effect of procedural and cognitive autonomy-supportive teaching on student learning and motivation during a 7th-grade reform-based science lesson on motion. In a 2 x 2 factorial design, the 4 treatment conditions featured high and low levels of procedural and cognitive autonomy support. As hypothesized, there was no effect of procedural autonomy support. However, to the authors' surprise--and in contrast with their hypotheses--students in the low cognitive autonomy-supportive conditions learned significantly more, perceived significantly more choice, and rated instruction as more positive than did students in the high cognitive autonomy-supportive conditions. Results are framed in the context of achieving reform in science teaching. (Contains 11 tables and 4 figures.)