This study involved the development of an instrument, the Science Career Predictor Scale (SCPS), which assesses seven factors thought to be involved with science career choices: teacher/counselor encouragement, participation in science-related hobbies and activities, academic self-image, science-related career interest, parental encouragement and support, the perceived relevance of mathematics and science, and mathematics and science ability. This instrument was administered to a sample of 522 middle and high school students, and a sample of 185 students from an historically black university, and the effects of such factors as sex, race, personal acquaintance with a scientist, and type of community (rural or urban) on the above-mentioned variables were ascertained using a multivariate analysis of covariance with age as the covariate. A separate study on a sample of 81 high school students looked at race and gender differences in critical thinking abilities as measured by the Watson-Glaser Critical Thinking appraisal, and how these abilities correlated with scores on the Science Career Predictor Scale. These studies produced several significant findings. Female subjects did produce significantly lower scores on the career interest factor. Black students actually had significantly higher science-career preference scores than their white counterparts. However, blacks scored significantly lower on the measure of critical thinking ability. Across both races and both sexes, however, the major factor affecting science-related career decisions appears to be personal contact with a scientist. The implications of these findings are discussed, along with possible strategies for increasing the participation of these groups in science.