This study proposed and tested a model based on stereotype threat theory. The hypothesis is that women who are exposed to a low percentage of women in a science program are more likely to endorse the gender stereotype that science is a male domain, which will in turn undermine their autonomous academic motivation. A total of 167 women university students enrolled in science programs participated in an 18-month longitudinal study. Results partially support our model. Although the low percentage of females in science programs was related to endorsement of the gender stereotype, there was no effect of prior stereotype endorsement on subsequent autonomous academic motivation. (Contains 1 table and 2 figures.)