Used kinematic measures to compare relative contributions of growing body dimensions, age, and walking experience in walking skill development in 9- to 17-month-olds, kindergartners, and college students. Found that with increased age, size, and experience, children's steps became longer, narrower, straighter, and more consistent, reflecting a narrower base of support and increasing control over the path of progression. Experience was a stronger predictor of skill improvement than was age. (Author/KB)