A mathematical model was employed to study the relative influences of interstitial osmotic pressure gradients, interstitial volume, lymphatic action and system geometry on the transcapillary exchange of fluid and plasma proteins within a modified Krogh cylinder tissue unit. The model includes a description of lymphatic behaviour and incorporates modified versions of the fluid and membrane transport equations to describe interstitial fluid flow under the influence of protein osmotic pressure gradients. The subsequent analysis suggests that these gradients have little effect on the overall hydrodynamics within the tissue. However, the properties of the draining lymphatic vessel and the radial dimension of the tissue cylinder exert strong influences on the magnitude and distribution of fluid and plasma protein fluxes across the capillary wall. The results of these simulations challenge current assumptions about transcapillary fluid flux distributions since they predict little exchange near the arteriolar end of the system in many cases. Further, as the radial dimension of the cylinder increases, the capillary moves from a state of fluid filtration along its entire length to one in which reabsorption occurs near the venular end of the blood vessel.