The goal of this study was to develop a survey instrument to measure transactional distance in secondary blended learning environments. This study resulted in a 35-item survey instrument, the Blended Learning Assessment Scale of Transactional Distance (BLASTD), which was tested using a convenience sample of secondary students (n = 222) at a secondary blended learning site. The research followed a methodology for scale development developed by Hinkin, Tracey, and Enz (1997), and was conducted through the following seven steps: (1) Item Generation; (2) Content Adequacy Assessment; (3) Questionnaire Administration; (4) Factor Analysis; (5) Internal Consistency Assessment; (6) Construct Validity; and (7) Replication. The initial survey was administered a semi-rural blended learning site in the pacific northwest. The gathered responses were then used in statistical analyses that included an exploratory factor analysis utilizing a scree plot and item response eigenvalues to identify the underlying dimensions of the BLASTD survey, and a Cronbach's alpha to establish the reliability of items and factors. Validity was examined by using a Pearson's product-moment correlation coefficient correlating the results of the BLASTD with the selections of the Huang, Chandra, Depaolo, Cribbs, and Simmons or HCDCS Survey. The final survey contained 35 survey items and the survey instrument took into account Moore's theory of transactional distance and is able to measure the dialogue between the instructor and student, the structure of the learning environment and educational learning opportunities, as well resulting student sense of separation or transactional distance. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]