The Cardiff acuity test was used in estimating the binocular and monocular visual acuity norms of 231 toddlers between 12 and 36 months. Mean binocular acuity increased from 4.5 to 1.2 min arc and monocular acuity from 4.5 to 1.4 min arc over the age range. Interocular acuity difference was not significant and for 99% of the children, the difference in acuity estimate was < or = 1/3 octave. Success rates ranged from 96 to 100% for binocular tests but fell to a range of 41-91% for monocular testing. Acuity assessment was fast and the intraobserver reliability was high. Age norms of visual acuity useful in clinical settings are presented for toddlers between the ages of 12 and 36 months.