The present study aimed to describe language development in children with Down syndrome, focussing on the relationships between gestural and vocal communication. The individual developmental trajectories of gesture production and its predictive role on later language development were analysed in a group of children with Down syndrome. Eight two-year-old children were followed for a two-year period until they reached the age of four years old. With regard to the developmental trends, two distinct patterns were found. Some children showed an increasing profile of gesture production, whereas others showed an inverted U-shaped profile or a stable production of gestures. Only the children in the second group showed a remarkable growth in their lexical abilities. Moreover, gesture production was identified as a reliable predictor of later vocabulary size when children were both 24 and 36 months old, and the production of crossmodal transitional forms (i.e., gesture-word associations) appeared to be a significant predictive index of their later two-word production.