Federal legislation such as No Child Left Behind requires greater focus and attention on the part of schools and school districts not only to make school improvements, but also to meet rigorous accountability requirements such as Adequate Yearly Progress (AYP) as determined by high student achievement guidelines. These requirements have compelled school principals to use accountability data to guide decision making for effective instruction. However, school leaders are prepared adequately to use data by professional development programs. If individuals in charge of the professional development of principals better understood the relationships between schools' successes as determined by accountability systems and their principals' perspective toward data use, preparation and professional development could be better designed and targeted to meet students' learning needs. The purpose of this study was to produce knowledge that can contribute to the improvement of professional development efforts in the use of data for school principals in El Paso County, a Texas-Mexico border community. This was accomplished by investigating five school principals' personal variables related to the use of data. These variables included: (1) principals' use of data, (2) principals' personal attitudes toward data, (3) principals' competencies with using data, (4) principals' instructional leadership self-perceptions, and (5) principals' professional development experiences (Torrence, 2002). A stratified random sample of sixty-five school principals from different elementary, middle, and high school levels from nine independent school districts in El Paso County responded to five dimensions of an instrument developed by Torrence (2002) to assess their views of data use and instructional leadership. These data was used to test thirty-five research hypotheses using three types of statistical analyses. The inter-relationships across all five principal personal variables were investigated by testing ten research hypotheses using a series of Pearson product-moment bivariate correlations. Statistical significance was found in nine cases. The differences in mean scores of principals in schools that met AYP and principals in schools that did not meet AYP by level of school (elementary, middle or high) for each of the five principal personal variables were investigated by testing fifteen research hypotheses. A series of independent sample t-tests were applied. Of the fifteen comparisons, principals of schools that made AYP outscored principals of schools that had not eight times. Differences were statistically significant. In four other comparisons, the differences approached statistical significance. Differences were more pronounced in elementary schools than in middle and high schools. Finally, the differences between two correlations by comparing the obtained inter-correlations of principals in this study to principals in Torrence's (2002) study for all five principal personal variables were investigated by testing ten research hypotheses. A series of Fisher-z transformations tests were implemented. Statistical significance was found in four cases. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]