This paper provides a comprehensive overview of adolescent career plans reported in PISA 2006. Its main focus is on the differences in the status and area of employment expected by girls and boys in high school. In almost all countries, girls lead boys in their interest in non-manual, high status professional occupations. This can be seen as a vertical dimension of gender segregation in occupational preferences. Students also differ by gender in selecting particular fields of employment within status categories. These differences make up the horizontal segregation of students' expectations and, in PISA 2006, are prominent in the gendered choices of specific subfields of science. Both the vertical and the horizontal dimensions must be considered to appreciate the cultural and institutional factors which promote and reinforce systematic divides in career choices of adolescent boys and girls. Although, in many countries, the proportions of girls and boys interested in a science-related career are comparable, the types of careers which appeal to each gender are markedly different. Few girls desire employment in computing and engineering, while careers in health services do not attract many boys. Leaving science-related employment aside, socio-cultural professions appeal to girls much more than boys. Remarkably, this pattern holds across all PISA-participating nations, although the size of the gender gap varies by country. The paper also presents an analysis of potential determinants of this gap, including student academic performance, course-taking patterns, socio-economic background, parental occupations, students' placement in vocational tracks, career information and career preparation in school. While all of these factors make separate contributions to determining the types of careers young people expect, none of them can fully explain the horizontal segregation of expectations by gender.