Spatial abilities are fundamental to human functioning in the physical world. Spatial reasoning allows people to use concepts of shape, features, and relationships in both concrete and abstract ways, to make and use things in the world, to navigate, and to communicate. Surgeons, pilots, architects, engineers, mechanics, builders, farmers, trades people, and computer programmers all rely on spatial intelligence. Several studies indicate that spatial ability can be improved if training with appropriate materials is provided. Most ninth grade students in Mississippi take a modular Technology Discovery course that includes a computer-aided design and drafting (CADD) shapes using spatial ability. In order to implement 3-dimensional software in curricula statewide, "Pro/Desktop[R] was made available through the "Design and Technology in Schools Programs" sponsored by the Parametric Technology Corporation. Evidence did not exist about the effectiveness of using 3-dimensional CADD programs to develop spatial ability. This study investigated whether selected instructional methods using 3-dimensional CADD software had an effect on the development of spatial abilities of ninth grade Technology Discovery students. (Contains 7 tables.)