This study arose from an interest in the possible presence of mathematics disabilities among students enrolled in the developmental math program at a large university in the Mid-Atlantic region. Research in mathematics learning disabilities (MLD) has included a focus on the construct of working memory and number sense. A component of number sense is the formation of a mental number line. This study looked at the mental representations of the number line in postsecondary developmental math students. It was found that the overall representation was linear, linear for three of four academic levels, and there were linear representations based upon gender. The presence of increased error rates on number line estimations between 23 and 39 needs to be explored. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]