Regional differences in the growth of Spanish children were studied by fitting the Preece-Baines Model I to cross-sectional stature data. The function parameters and derived biological variables were used to compare children from seven different studies. Regional differences in growth are interpreted as a result of a geographic variation among Spanish provinces in demographic, public health and nutritional conditions. There are differences between urban samples depending on region. Adult stature (h ) and the pattern of growth differ between urban and rural populations from the interior lands. Males from urban Extremadura, Barcelona and the Basque Country show the tallest adult statures. Adult statures of males from Segovia, Extremadura emigrants and Cuenca are not only the lowest, but the growth pattern shows delay in estimated ages at take-off and PHV compared to the other populations. Estimated age at PHV is later for all male samples compared to Vizcaya, except for the sample of Barcelona-I. Females from Barcelona-II, Segovia and the Basque Country show the tallest adult statures (h ). All of the female samples, except that of urban Extremadura, have an earlier estimated age at PHV compared to the sample from Vizcaya. © 1995 Wiley-Liss, Inc.