In the natural situation, the piglet’s transition from a wholly milk to a wholly non-milk diet (weaning) is gradual and paralleled by progressive, appropriate modification of gut structure. The sow’s milk provides nutritional, trophic and immune support throughout this transition thereby mediating intestinal exposure to novel nutrients and pathogenic agents whilst the gut structures necessary to process them appropriately are maintained and developed. Commercial weaning deprives the piglet of lactogenic support and simultaneously necessitates the marked acceleration of gut development if piglet health and growth are to be maintained. Intestinal mass, growth (Slade and Miller 2000) and fractional protein synthesis rate (Ks) increase significantly following weaning (Le Dividich and Seve 2000). Correspondingly, the nutrient cost of post-weaning intestinal development is high. However, weaning is invariably associated with a dramatic reduction in feed intake and, in turn, with a decline in gut efficiency characterised by a reduction in villus height and an increase in crypt depth. Perversely, the gut morphology of the weaner thus appears a limiting factor in its own development. Here we introduce a simple histological method for estimation of individual crypt-villus structure surface area and then, in conjunction with conventional histomorphological measurements, use this to relate piglet performance, nutrition and gut morphology.