Several studies have been carried out recently to learn more about sexrelated differences in mathematics achievement. A major question addressed by these studies is why fewer females than males continue studying mathematics beyond those courses required for high school graduation or college entrance. This paper addresses this question through a secondary analysis of data from the National Longitudinal Study of Mathematics Achievement (NLSMA) (Romberg & Wilson, 1969). The analysis identifies sex-related differences in selected variables believed to influence student decisions to continue the study of mathematics. The resulting findings are in remarkable agreement with current studies (Armstrong, 1980; Fennema, 1977; Fennema & Sherman, 1977; Casserly, Note 1; Steel & Wise, Note 2) and suggest the validity of analyzing extant data for insights into continuing educational questions. Further, although the NLSMA study was carried out in the 1960s, because of its extensive nature, it behooves us to learn what it tells about sex-related differences that may have been present at that time. Indeed, the students in the NLSMA study are the teachers of the 1980s.