A high school teacher was studied who was known to have begun implementation of a modern paradigm of mathematics education, as described in the "Curriculum and Evaluation Standards for School Mathematics" and the "Professional Standards for Teaching Mathematics," both by the National Council of Teachers of Mathematics. His instructional and assessment practices are described, and his teaching practices are profiled according to the recommendations of the standards document as he struggled toward more complete implementation. Interviews, observations, and collections of teacher-used materials provided the information for the study. The subject had been teaching for 20 years, during which he worked on a master's degree in mathematics education. Classes in problem-solving and educational psychology in his studies led him to question his teaching practices. He attempted changes in his teaching practice that were implemented in a spotty fashion and were difficult to maintain. This subject found implementation of the "Standards" to be a long-term project, which required time for reading, discussion, and reflection, as well as support from many sources. (SLD)