24 h oral intake and intestinal output were studied in 15 patients with a short residual length of jejunum and no colon. 8 patients showed a net secretory, and 7 a net absorptive response to food. In secretors, daily intestinal output exceeded oral intake (mean 2.3 kg wet weight, and 233 mmol sodium). Long-term parenteral fluid and electrolyte replacements were needed only in those with a secretory response. Jejunal length inversely correlated with net intestinal output of fluid, sodium, potassium, and with percentage energy absorption. A secretory response was observed if jejunal length was less than 100 cm and was reduced by gastric antisecretory drugs and octreotide.