Preferential looking using square waves is commonly used to measure visual acuity of infants. Since sinewave gratings have the advantage of presenting only a single spatial frequency, we completed a study to develop and validate a set of acuity cards using sine waves. The subjects were 83 children (mean age=41.5 months, range=3 to 69 months). The sine-wave cards were compared with Teller cards. Identical visual acuity was determined in 83% of the cases. Wilcoxon non-parametric analysis provided no evidence to reject the null hypothesis of equal visual acuities between the two methods. We conclude that sine-wave cards may be used to measure the preferential looking acuity of children. © 1990 American Academy of Optometry.