The transfer constant K trans is commonly employed in dynamic contrast-enhanced MRI studies, but the utility and interpretation of K trans as a potential biomarker of tumor vasculature remains unclear. In this study, computer simulations based on a comprehensive tracer kinetic model with multiple pathways was used to provide clarification on the interpretation and application of K trans. Tissue concentration-time curves pertaining to a wide range of transport conditions were simulated using the multiple-pathway (MP) model and fitted using the generalized kinetic (GK) and extended GK models. Relationships between K trans and plasma flow F p, vessel permeability PS and extraction rate EF p under various transport conditions were assessed by correlation and regression analysis. Results show that the MP model provides an alternative two-tier interpretation of K trans based on the vascular transit time. K trans is primarily associated with F p and EF p respectively, in the slow and rapid vascular transit states, independent of the magnitude of PS. The relative magnitudes of PS and F p only serve as secondary constraints for which K trans can be further associated with EF p and PS in the slow and rapid transit states, respectively.