In an earlier report (Harman, Humphrey, & Goodale, 1999), we demonstrated that observers who actively rotated three-dimensional novel objects on a computer screen later showed faster visual recognition of these objects than did observers who had passively viewed exactly the same sequence of images of these virtual objects. In Experiment 1 of the present study we showed that compared to passive viewing, active exploration of three-dimensional object structure led to faster performance on a "mental rotation" task involving the studied objects. In addition, we examined how much time observers concentrated on particular views during active exploration. As we found in the previous report, they spent most of their time looking at the "side" and "front" views ("plan" views) of the objects, rather than the three-quarter or intermediate views. This strong preference for the plan views of an object led us to examine the possibility in Experiment 2 that restricting the studied views in active exploration to either the plan views or the intermediate views would result in differential learning. We found that recognition of objects was faster after active exploration limited to plan views than after active exploration of intermediate views. Taken together, these experiments demonstrate (1) that active exploration facilitates learning of the three-dimensional structure of objects, and (2) that the superior performance following active exploration may be a direct result of the opportunity to spend more time on plan views of the object.