Interviews were conducted with 20 out of 40 primary teachers who, 3 or 4 years earlier, had participated in inservice workshops on Cognitively Guided Instruction (CGI), a research-based approach that emphasizes using children's mathematical knowledge to teach mathematics and who had consented to do the interviews. Although all but one teacher were still using CGI to teach mathematics, their use varied widely from occasionally or supplementally to mainly or solely. Teachers' use was significantly related to ideas about what it means to "know" mathematics, how students learn mathematics, and what responsibilities and roles teachers and students have in learning mathematics. Three patterns of change in CGI use emerged: Group 1 teachers reported a steady, gradual increase to reach their current main or sole use of CGI; Group 2 reported having never used CGI more than supplementally or occasionally and were settled in that use; Group 3 reported using CGI in earlier years but now using it only supplementally or occasionally. These patterns of use were related to the meanings that teachers had constructed for CGI. In their espoused beliefs and practices, Group 1 described CGI conceptually; Group 2 described CGI procedurally, as using manipulatives or word problems; while Group 3 showed a marked incongruity between their espoused beliefs and espoused practices. (Author/MDH)