The enacted curriculum and classroom artifacts of a full unit of instruction from three subject areas (biology, chemistry, and physics) at two levels of instruction (regular and advanced) were analyzed for the presence and degree of mathematics and critical thinking. These characteristics were selected from a review of the literature on college science faculty's views of best student preparation. Classes were grouped and compared by subject area and by level of science class. Varying degrees of critical thinking and mathematics were found to be present in the six observed classes, but both characteristics were found in all of the observed units of instruction. Comparisons of the statistical and practical differences found the greatest differences when comparing mathematics by subject area. These differences were not due to within subject area differences. Comparisons found the greatest similarities when comparing critical thinking by level of instruction. It was found that classroom pedagogy was a more important factor than subject area or level of instruction in determining the degree of alignment of classroom instruction with respect to the presence and inclusion of mathematics and critical thinking. Overall, there was a common lack of explicit instruction in both mathematics and critical thinking among all observed units of instruction. These findings support the need for more explicit mathematics and critical thinking instruction within science classes. Also, it is recommended that pre-service and practicing science teachers are prepared with the knowledge and methods of best mathematics instruction to better incorporate these strategies within and alongside their science instruction. [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.]