Researchers have found that 3D spatial skills are critical to success in a variety of careers, particularly in engineering and science. For engineering, the ability to mentally rotate objects in space has been found to be of particular importance. Unfortunately, of all areas of cognition, 3D spatial skills still exhibit some of the most robust gender differences favouring males, and the most pronounced gender differences are in the area of mental rotations. For this reason, poorly developed 3D spatial skills could be a hindrance to the success of women in engineering. University educators are quick to recognise deficiencies in math and chemistry, and many US universities have developed remediation programs for students with weaknesses in these areas. At a time when we are actively recruiting women for engineering programs, however, it is important to consider all possible barriers to their success. At Michigan Technological University (MTU), we have been offering a special course aimed at improving the 3D spatial skills of engineering students, particularly women, since 1993. This paper will summarise the findings obtained over the past decade at MTU in improving the 3D spatial skills of engineering students. The paper will also feature improvements in student success that we have achieved, especially for women, through implementation of this bridging course.