This report describes a 9-month, nationwide project which investigated the teaching strategies and teacher attitudes which successfully encouraged girls in science. Subjects included 205 females and 147 males from seven high schools. In addition to analyzing instructional techniques, classroom climates, and teacher-student interactions, a selected sample of former and current students received a variety of instruments which assessed attitudinal, cognitive, and socio-cultural variables. Results obtained from the case studies and survey instruments indicate that teachers who successfully encourage girls in science maintain well-equipped, organized, and perceptually stimulating classrooms, are supported in their teaching activities by parents of their students, are respected by current and former students, use non-sexist language and examples, include information on women scientists, use a variety of instructional strategies, stress creativity and basic skills, and provide career information. Factors which discourage girls in science include high school counselors who do not insist on further courses in science and mathematics; lack of information about science-related career opportunities and the prerequisites for them; sex-stereotyped views of science and scientists fostered by textbooks, media, and many adults; lack of development of spatial ability skills; and fewer experiences with science activities and equipment that are stereotyped as masculine. (JN)