As the first step in a study of mucosal polyamine metabolism during intestinal adaptation, we have measured mucosal polyamine concentrations at different sites along the normal rat intestine. Putrescine, spermidine, spermine and cadaverine were measured by spectrofluorometric analysis after thin-layer chromatography of their dansylated derivatives. Spermidine was present in the largest amounts at each of the sampling sites. The ratio of the concentration of spermidine to that of spermine paralleled the established pattern of cellular proliferation in the normal intestine as did the putrescine concentration (nmol per 10 cm) which decreased from duodenum to colon. These results provide the essential background to an assessment of the role of polyamines in the intestinal adaptive response.