The present study examined how preschool children integrated the information displayed successively through a slit into a whole reasonable picture. Children aged 3, 4, and 5 years old were asked to name nine kinds of line-drawings while being moved behind a stationary vertical slit. An adequate speed for perceptual integration was measured (Exp. I). The ability to integrate the piece-meal information improved with age and at all ages, the picture was integrated more easily when the slit became wider. Distortion rates in moving figures (circle and diamond) viewed through a slit were measured for 4, 5, 8, and 10 years old children (Exp. II, III). As the velocity of moving figures became slower, the figures were observed more elongated. Age differences were not so clearly shown in distortion rates, but at every speed 10 year-old children always observed circles more elongated than other children.