1. Uptake of L-[2(n)-3H]methionine and 3-O-methyl[14C]-D-glucose (3MG) from jejunal loops in vivo was investigated in germ-free (GF), gnotobiotic (GN) and conventional (CV) chicks aged between 2 and 4 weeks.

2. Body-weight gain was less, and intestine weight per unit length greater, in CV and GN birds than in corresponding GF birds.

3. Uptake of both nutrients was less in CV and GN birds when calculated per g intestinal tissue, but no difference was found between any of the groups when uptake was expressed per unit length of intestine.

4. Concentration of methionine in mesenteric and cardiac blood was higher, and amounts in the intestinal wall lower, in CV chicks than in corresponding samples from GF birds.

5. Concentration of 3MG in mesenteric blood was similar in both environments but it was higher in cardiac blood and lower in the gut wall of CV birds.

6. It was concluded that uptake of methionine and glucose is not impaired by the presence of micro-organisms in the gut.