This first report from a population-based postnatal growth study of 3650 healthy Swedish subjects born at full term provides new reference values for height and weight and shows that over the last 20 years there has been a small secular trend in height (0.2-0.4 SDS over the whole age range) in Sweden in both boys and girls. Within this cohort, 111 (3.1%) were of low birth weight (below -2 SDS) and 141 (3.5%) were of low birth length (below -2 SDS); 54 (1.5%) were both light and short at birth. Of the children born small for gestational age, 87% showed full catch-up growth within 2 years of life. They attained puberty at a normal or early age and reached a mean final height of -0.7 SDS. The remaining subgroup of 13% born small for gestational age remained below -2 SDS throughout childhood and reached puberty somewhat early. Their mean final height was -1.7 SDS. The current data set is too small to identify possible background factors, but it is being expanded with this objective in mind.