This study examined how instructional challenges presented by gifted students shaped teachers' instructional strategies. This study is a qualitative research grounded in a social constructivist framework. The participants were three high school science teachers who were teaching identified gifted students in both heterogeneously- and homogeneously-grouped classrooms. Major data sources are classroom observations and interviews. Data analysis indicated that these science teachers developed content-specific teaching strategies based on their understanding of gifted students, including: (a) instructional differentiation, e.g., thematic units, (b) variety in instructional mode and/or students' products, (c) student grouping strategies and peer tutoring, (d) individualized support, (e) strategies to manage challenging questions, (f) strategies to deal with the perfectionism, and (g) psychologically safe classroom environments.