A total of 3,681 students in the second, fifth, and eighth grades at 24 integrated elementary schools completed a brief questionnaire listing the sex and race of their four best friends at school. Racial discrimination in friendship choices was related to the relative frequency of the student's racial group within a grade. Blacks, but not whites, discriminated most on the basis of race when they constituted from 20 to 80% of the relevant population. Possible reasons for this relationship between proportionality and discrimination are discussed. (Author)