It is widely accepted that the maturation of the extrastriate cortex is not completed before late puberty. To gain insight into the functionality of the extrastriate cortex during normal development, we tested a group of 21 children (age 6-16 years) on their ability to detect motion-defined forms. With a two-alternative forced-choice procedures we determined thresholds and visual half-field asymmetries (i.e., left vs right) for detection of relative motion. It was found that children had higher thresholds than adults. Furthermore, children had more difficulty with the detection of motion in the left than right half-field, whereas the control group of 33 adults (age 21-55 years) performed similarly in both visual half-fields. These results are discussed in the light of a hemispheric asymmetry in the maturation of the extrastriate cortex.