Speakers gesture at high rates when explaining their solutions to spatial problems. The present work investigates one possible explanation for why speakers gesture so frequently during spatial problem solving, namely, that when speakers imagine the problem components in motion, they are particularly likely to gesture. We compared speakers gesture rates as they actively solved a mental rotation problem and as they described the end state of the problem. Speakers gestured at a higher rate in the rotation condition. Thus, it appears that thoughts about the problem pieces in motion in the rotation condition do lead to increased gesture rates.