Teaching computer science (CS) in high schools, rather than just programming or even computer literacy, is important as a means of introducing students to the true nature of CS, and enhancing their problem-solving skills. Since teachers are the key to the success of any high school educational initiative, any discussion of high school programs must consider the teachers, and specifically the teacher preparation needed to make the implementation of such programs possible. However, there is scant research on CS teacher education, probably because CS is a relatively young discipline. Very few of the publications in the area of CS teacher preparation are research-based. Most are descriptive papers, including recommendations for specific programs or courses. The purpose of this survey is to import from what is already known in other disciplines in this context. We therefore examine the body of research on teacher education in other disciplines, especially in mathematics and science, to shed light on important challenges for CS teacher education and draw some initial conclusions regarding CS teacher preparation programs.