The fast preferential looking procedure was used to obtain measures of acuity in a group of infants without visual problems whose ages spanned the 1st year of life. The results show an increase in acuity on horizontal and vertical square wave gratings from about 6/360 Snellen at 4 weeks of age to about 6/18 at 1 year. Acuity on obliquely oriented gratings (045) increases more slowly so that by 1 year of age it is only 6/36.