This paper, presented at the 1979 meeting of the American Educational Research Association (AERA), investigates the affective characteristics of 120 junior high school students who participated in one or both of the first two programs of Minnesota Talented Youth Mathematics Project (MTYMP). The first year program of 1976-77 was in algebra I and II, and the second year program of 1977-78 was in geometry-trigonometry. Students were selected by their aptitude test scores in an annual talent search. No sex differences in achievement among these extremely talented youth have been found. However, the attrition by girls, especially after the first year, has been disproportionately high. Also, the attitudinal changes do exhibit sex differences. These results suggest that affective variables do affect the motivation and future plans of talented students. (HM)