Hand function deficits in hemiplegic children are a major cause of disability, but there is a lack of appropriate instruments for evaluating the evolution of this deficit over time and for verifying the efficacy of its treatment. We evaluated changes in upper limb function in relation to age and the course of individual rehabilitation treatment in 20 children (13 males and 7 females) who were first seen within the first four years of life and subsequently followed until a mean age of 13 years and four months (range, 11-17 years) in accordance with a diagnostic/rehabilitation program initiated in our division in 1989. All of the children were treated by us; those whose paretic upper limb functioned well were not treated in any specific or directed manner. The protocol involved a qualitative evaluation of the spontaneous use of the paretic hand and a quantitative evaluation of grip. Analysis of the results revealed an age-related global improvement over time, occurring within the first five years of life and more pronounced in terms of grip than spontaneous use. This finding makes our protocol more specific than those currently used because it more reliably establishes the real capacity to use the paretic hand in different situations of everyday life. The most important changes concerned the children with more impaired functional capacity, whereas the children who presented with good functional skill retained this capacity over time, thus confirming the initial decision not to treat them.