The purpose of this study was to investigate the effects of the Casio 9850 and the TI-85 graphing calculators on college students' procedural skills and conceptual understanding in two different developmental mathematics courses. The courses used in this study were Elementary Algebra and Intermediate Algebra. Both the non-graphing calculator group and graphing calculator group were taught with the same goals. The students in the graphing calculator group were allowed to use the graphing calculator in place of performing paper and pencil procedures in class and on all tests. Students in the control group classes did not have a graphing calculator in class or on the tests, although all students were required to have access to a scientific calculator. The tests used in the study were two researcher-generated tests for Elementary Algebra and Intermediate Algebra. The procedural questions on the tests were similar to the Compass Placement Test (CPT), and the conceptual questions on the test were similar to the Core Learning Goals Test (CLGT). The test questions were reviewed and critiqued by a panel of five experts in the field of mathematics education who are familiar with the distinction between procedural skills, conceptual understanding, and the content of these courses. The tests were scored with an analytical scoring rubric. A Cronbach's Alpha test showed that the tests were reliable. Results of the pre-test to post-test analysis showed that there were statistically significant gains in procedural skills and conceptual understanding for both the Elementary and Intermediate Algebra graphing calculator sections (p<.0001). Significant results were also found in comparing the amount of gain in procedural skills and conceptual understanding for the non-graphing calculator and graphing calculator sections. There were significant increases in gains of procedural skills and conceptual understanding for the graphing calculator group versus the non-graphing calculator group enrolled in Elementary and Intermediate Algebra (p<.005). Suggestions for teaching using graphing calculators and recommendations for further study conclude the dissertation. Copies of the tests administered to the subjects, a graphing calculator supplement, and course syllabi are also attached. (Contains 97 references.) (ASK)