We have used a spatial two-alternative, forced-choice staircase technique to measure contrast sensitivities for sinusoidally modulated gratings. Subjects, all of whom were untrained observers, consisted of children of ages 2-16 yr and adults. Our testing method was completely successful with children who were over 3.5 yr but failed with those below 2.5 yr. Mean contrast sensitivities of the youngest group from which data were obtained (2.5-4.5 yr) were 0.35 log units lower than those of adults. However, there was very little difference between these two groups in the middle range of spatial frequencies tested. A gradual increase with age of contrast sensitivities was found up to about 8 yr. This change is probably due to a combination of neural development and non-visual factors.