Reaching and grasping skills have been described to emerge from a dynamic interaction between intrinsic and extrinsic factors. The aims of the study were to investigate the effect of such intrinsic factors as age and Down syndrome on the development of reaching and grasping skills and on overall gross motor skill, and to test the influence of the overall level of gross motor skill on the development of reaching and grasping. Seven infants with Down syndrome (DS) and seven infants with typical development were assessed at the ages of 4, 5 and 6 months. The following variables were analyzed: straightness index, mean velocity, movement units and deceleration time (for reaching movements), grasping frequency and AIMS scores. Intrinsic factors such as age and DS were found to influence the development of reaching, grasping, and of the overall level of gross motor skill. The overall level of gross motor skill was observed to influence grasping. (Contains 4 figures.)