This study examines the effects of using different classes of ratios on adolescent performance on proportionality problems. Problems of the form a/b = c/x varied on four dimensions: size of a/b, equality or inequality of b and c, complex or simple fractions, and form of the test. Tests consisted of six proportionality problems involving sizes of stick figures. Thirty-two seventh-grade students served as subjects. Responses were scored on the 10-point scale developed by Karplus, and the resulting data were submitted to several analyses of variance. Results indicated that only one-fourth of the problems were solved by strategies based on understanding of proportionality. Subjects were able to solve some of the easier problems, suggesting that they had (or were developing) some intuitive understanding of proportionality. The author suggests that content of a proportionality task may strongly affect students' performance on it. (SD)