The objective of this study was to classify intrauterine growth-retarded (IUGR) newborn babies from an urban region in Brazil into four different subtypes, according to their weight, length, and ponderal index (PI). Three hundred and fifty-six (356) babies were differentiated by this classification into IUGR subtypes A (short length and adequate PI), B (adequate length and low PI), C (short length and low PI), and D (adequate length and adequate PI), by the Lubchenco weight, length, and PI for gestational age standards. Gestational age of the babies was determined by the Capurro method. Anthropometric measurements were taken according to the Jelliffe and Jelliffe recommendations. Ninety-eight per cent of the IUGR babies included in the study were type I (proportional): 48 per cent of them were subtype A and 50 per cent subtype D (slightly thin). Subtypes B and C comprised 1.4 per cent and 0.6 per cent of the babies respectively. This classification of IUGR is of great importance, considering that these four subtypes probably reflect the stages of pregnancy at which the babies were affected by adverse growth and development factors. The risk factors for the different subtypes of IUGR, and examination of their predictive value for subsequent morbidity, growth, development, and mortality, will be of interest.