The career aspirations and the factors influencing career decisions were investigated for a group of extremely precocious females to determine why some enter math/science careers and others do not. Using the multiple-case study approach, 15 mathematically precocious females' career paths were characterized. These females had scored before age 13 at least 700 on the Scholastic Aptitude Test-Mathematics (SAT-M) (frequency: top 1 in 60,000);Questionnaires completed at age 13, in 8th grade, and after high school graduation were used; in-depth telephone interviews at 19 to 21 years provided further data. Extremely mathematically precocious females have focused career goals by age 18; two-thirds had entered math/science fields by age 19-21. Their career and educational aspirations were high, with 73% aspiring toward the doctorate degree from prestigious institutions and 100% toward professional occupations. Typical lifestyle expectation was to have a full-time career with marriage and family options. The 700M females aspiring to careers in math/science versus other careers differed along several dimensions. Both groups exhibited achievement-related personal traits; especially for the math/science group, they did not sex-type themselves or occupations. The math/science career group had greater interests in math and science during adolescence, while the other career group exhibited stronger interests and abilities in the verbal areas. Family influences on career decisions were important for both groups, but were stronger for those who chose math/science careers. Career choices often corresponded to their father's career field. Both groups achieved academically at an outstanding level; all were accelerated, (all but two skipped a grade). Their solid academic preparation enabled them to enter any career track, especially the nonmath/science career group. Guidance activities were not viewed as helpful by 700M females. Yet, most reported that a significant person (e.g., a teacher or mentor) or an event had affected their career decisions. These mathematically precocious females ultimately made their career decision based on their interests, which evolved from early family influences and educational experiences.