Linear growth during the first three years of life can be represented mathematically in terms of the "ICP-growth model", using a combination of a quickly decelerating Infancy component with the addition of a slowly decelerating Childhood component, the latter acting from the second half of the first postnatal year. The growth pattern for supine length of four children with growth hormone (GH) deficiency is related here to the first two components of this growth model. Basically, all four infants displayed a pattern in line with the exponential shape of the Infancy component to the age when GH therapy was initiated. This observation indicates the existence of the Infancy component as it has been adopted for the ICP-model, and also that it represents the part of postnatal linear growth which seems to be independent of GH. The onset of the Childhood component in healthy subjects has been observed as an abrupt increase in growth rate during the second half of the first year of life. A similar abrupt increase was observed in this study at the time of the initiation of GH therapy (16-27 months). This observation gives some further empirical support to the hypothesis that the child's age at onset of the Childhood component defines the as yet undetermined age at which GH begins to exert a significant influence on linear growth. ICP-based growth charts provide an improved instrument for early detection of GH deficiency.