Spatial visualization is considered to be one of seven human intelligences and is an active topic in educational research. Based on previous research, two distinct themes emerge: 1) well-developed 3-D spatial skills are critical to success in STEM fields, and 2) the 3-D spatial skills of women typically lag significantly behind their male counterparts. Understanding the need for training for some individuals, particularly women, Michigan Tech implemented a spatial skills course in 1993 with NSF support. This course has been shown to have a significant impact on the retention of female engineering students over the past ten years. In 1998, MTU received funding from NSF to develop multimedia software and a workbook aimed at improving 3-D spatial skills. These user-friendly, gender-neutral materials have been proven to develop the 3-D spatial skills of first-year engineering students. This paper presents preliminary findings when testing these materials in STEM fields outside of engineering and pre-college students in middle and high school.