Postnatal growth was followed in a population‐based group of 123 small‐for‐gestational‐age (SGA, birth weight<‐2 SD) children (66 boys and 57 girls) to four years of age in order to determine the incidence and time of catch‐up growth. Gestational age was determined by ultrasound in gestational weeks 16–17 in all pregnancies, thus eliminating the problem of distinguishing between SGA and preterm infants. Infants with well‐defined causes for slow growth rate, i.e. those infants with chromosomal disorders, severe malformations, intrauterine viral infections or cerebral palsy, were excluded. The boys showed an extremely fast weight catch‐up, 85% of them reaching weights greater than ‐2 SD at the age of three months and remaining above this level to the end of the study period. Such a fast catch‐up growth was observed in only two‐thirds of the girls, but at four years of age 85?4 of the girls were also above ‐2SD. Length catch‐up was more gradual than weight catch‐up. Of the boys, 54% had lengths below ‐2 SD at birth, 26% at 1 year of age, 22% at 2 years of age, 17% at 2.5 years of age and 11% (n= 8) at 4 years of age. Corresponding figures for girls were: 69% at birth, 28%) at 1 year, 15% at 2 years, 12% at 2.5 years and 5%) (n =3) at 4 years. At 4 years of age, only six boys and three girls remained below ‐2 SD for both weight and height. We conclude that in Sweden the prognosis for catch‐up growth for an SGA child, when children with well‐defined causes of growth disturbances are excluded, is very good and it is extremely rare for the child still to have a hei