This Research Brief focuses on the qualifications of teachers in science and mathematics as well as history, in grades 7-12 for the 2003-04 school year. The subjects of science and mathematics were selected because of continuing concerns in the United States over the high need for individuals with advanced knowledge and skills in these subjects. History was selected because of its high enrollment rates. Analysis found that 45 percent of secondary-level science and mathematics students as well as 53 percent of history students were taught by teachers with the highest qualification (with both an in-field major and an in-field regular state certification) in the 2003-04 school year. On the other hand, 26 percent of science or mathematics students and 12 percent of history students were taught by teachers with neither qualification. Students in lower poverty schools as well as students taught by veteran teachers were more likely to be taught by in-field teachers with an in-field major or certification. However, among students with teachers with the lowest qualifications (i.e., those with neither an in-field major nor certification), our analyses suggest that newer teachers' qualifications may be less far out-of-field than veteran teachers'. This may suggest some possible improvement in teachers' qualifications among the least qualified newer teachers, although further research is needed on this topic. (Contains 2 tables and 10 notes.)