The objective of this study is to examine factors influencing student achievement in Greece at the end of secondary schooling with special emphasis on the national examination, based on which selection in higher education is determined. The identification of these factors and their hierarchical contribution to achievement is investigated in a model which includes three subsequent stages involving: (1) achievement of applicants, (2) achievement of all successes in higher education, and (3) achievement of successes in university education. The data on which this study is based are derived from a 10 percent random sample of high school students throughout Greece. Factors addressed include in-school achievement, national examination achievement, school and teacher characteristics, personal characteristics, family characteristics, previous school achievement, and aspirations (curriculum track). Results show that achievement in high school is related more to previous school attainment and less to family social characteristics or personal characteristics while achievement in the national entrance examination is related primarily to curriculum track, previous attainment, followed by family social characteristics. Statistical tables reflecting multiple regression and correlation analyses on all factors are appended. (Author/EGS)