A significant fraction (≈ 50%) of methionine (Met) in the diet of weaned pigs is retained by the portal drained viscera (Stoll, et al. 1998). The consequent reduction in extraintestinal availability of Met may compromise piglet performance. Met regeneration in hepatic and renal tissues is achieved through combination of a methyl group from either N5-methyl-tetrahydrafolate or from betaine (trimethyl-glycine) with the Met derivative homocysteine. Supplementing the diet with betaine might therefore improve extraintestinal Met availability and piglet performance. Furthermore, betaine is an osmolyte and has been shown to stabilize or protect the intestinal epithelial structure of broilers under conditions of intestinal stress (Kettunen, et al. 2001). Provision of supplementary betaine in the diet of the newly weaned pig may thus reduce the extent of small intestine (SI) morphological degeneration characteristic of the early post-weaning period. The study reported here was designed to test these hypotheses.