A problem within science education in the United States persists. U.S students rank lower in science than most other students from participating countries on international tests of achievement (National Center for Education Statistics, 2003). In addition, U.S. students overall enrollment rate in high school Advanced Placement (AP) physics is still low compared to other academic domains, especially for females. This problem is the background for the purpose of this study. This investigation examined cognitive and motivational variables thought to play a part in the under-representation of females in AP physics. Cognitive variables consisted of mathematics, reading, and science knowledge, as measured by scores on the 10th and 11th grade Florida Comprehensive Assessment Tests (FCAT). The motivational factors of attitude, stereotypical views toward science, self-efficacy, and epistemological beliefs were measured by a questionnaire developed with question taken from previously proven reliable and valid instruments. A general survey regarding participation in extracurricular activities was also included. The sample included 12th grade students from two high schools located in Seminole County, Florida. Of the 106 participants, 20 girls and 27 boys were enrolled in AP physics, and 39 girls and 20 boys were enrolled in other elective science courses. Differences between males and females enrolled in AP physics were examined, as well as differences between females enrolled in AP physics and females that chose not to participate in AP physics, in order to determine predictors that apply exclusively to female enrollment in high school AP physics and predictors of an anticipated science related college major. Data were first analyzed by Exploratory Factor Analysis, followed by Analysis of Variance (ANOVA), independent t-tests, univariate analysis, and logistic regression analysis. One overall theme that emerged from this research was findings that refute the ideas that females have lower achievement scores, lower attitude, lower self-efficacy, and more stereotypical views regarding science than males. Secondly, the only significant differences found between males and females enrolled in AP physics were for stereotypical views toward science and one factor from the epistemological views questions, both of which favored females. Although the non AP boys significantly outscored non AP girls on science FCAT scores, the only other significant differences found between these groups of students were related to attitude, with the girls scoring higher than the boys on both counts. There were significant differences found for numerous variables between AP and non AP females, however, most of the same differences were found between the two ability groups of male students as well. This leads to the conclusion that these factors certainly play an important role in AP physics enrollment for both genders. But the few significant differences found exclusively between the two female ability groups; reading ability, stereotypical views toward science, and the epistemological beliefs regarding branches of physics being related by common principles and aspects of physics need to be inferred instead of directly measured, may play a more important role in increasing enrollment numbers of females.