In this study we investigated the influence of lymph flow on chylomicron transport. We examined the effects of varying the hydration of the interstitial matrix on chylomicron appearance time and on lymphatic lipid transport rate when a lipid test meal containing oleic acid and 1-monoolein was infused intraduodenally at a constant rate. The three groups of rats tested were control rats (normal interstitial hydration), rats receiving intravenous saline infusion (expanded interstitial matrix), and rats with an attenuated water absorption rate (dehydrated interstitial matrix). This study shows that lymph flow has a profound effect on intestinal chylomicron transport. As lymph flow increased, the chylomicron appearance time (time between the placement of radioactive fatty acid into the intestinal lumen to the appearance of radioactive lipid in the central lacteal) was reduced. When lymph flow exceeded 40 microliter/min, the chylomicron appearance time reached a minimum value of 13.6 min. This minimum chylomicron appearance time probably represents the time required for assembly of absorbed lipid, formation of chylomicrons, and their subsequent discharge into the lymphatics. The chylomicron appearance time lengthened as lymph flow fell. The results of this study underscore the necessity of using steady-state lymphatic lipid output data to assess factors affecting the cellular packaging and release of chylomicrons in the small intestine.