A study followed 445 Wellesley College (Massachusetts) women students matriculating in 1991 through their college years to isolate factors associated with persistence in math and science. Data were gathered through three surveys (at orientation, at the end of the sophomore year, and before graduation) and in focus groups over the 4 years of the study. Four possible pathways in science were examined: "never", "leaver", "joiner", and "always." Slightly over half fell into the first group; "leavers" comprised 22 percent; "joiners" were 4 percent; and "always" consisted of 18 percent. Characteristics of each group are discussed, with special focus on students leaving science and mathematics. It was found that members of this group tended to have lower high school grades in math and science, lower entrance examination math scores, and lower college grades in science and math. "Leavers" also reported lower levels of interest in science and lower mathematical ability, and were less likely to have a parent with an advanced degree than students who stayed in math and science. "Leavers" said they left science because they found other fields more interesting and because laboratory work required too much time. Findings suggested that the culture of science at Wellesley does not appear to discourage students. (MSE)