Birth weight and gestational age data from 5,418 infants born in the Maternal Hospital "Valle de Hebrón" during 1984, were retrospectively reviewed. 295 infants (5.4%) were excluded for different reasons. Tabulated data of the 5,123 remaining cases were used to design a representative chart of this population of infants. Simultaneous inclusion in the chart of +/- 2 SD curves and 10th and 90th percentile curves, allows us to establish an easy distinction between the low birthweight infants with moderate intrauterine growth retardation and those with a severe delay. This distinction may be clinically important. Data collecting methods for designing intrauterine growth charts are also discussed.